2. The Acquisition, Representation and Reconstruction of
Printed Music by Computer: A Review
The varied applications of computers to music include sound synthesis, computer-assisted composition, computer-aided instruction, music analysis and music printing. In each application there exists a dividing line between music as sound and as print. This boundary delineates the present study, which deals only with the graphical record, from aspects of sound synthesis and computer-assisted composition. For the latter, the reader is directed to frequent articles in the Computer Music Journal and the recent review by Yavelow [Yavelow 1987], which also includes a useful glossary of terms used in applications of computers to music. Within the subject of printed music, this review and the subsequent chapters concentrate, except where specified, on conventional Western music.
The three sections of the chapter heading - acquisition, representation and reconstruction of printed music - might well be supplemented by computerized music-setting, i.e., the design of software to implement the processes which normally fall to the music engraver. However, two major works of the literature [Gomberg 1975] [Byrd 1984] have specifically covered the topic of computerized music-setting in great detail, including fairly recent developments. This chapter therefore touches on matters connected with music-setting only where these are inextricably linked to other subjects within the province of this review.
Section 2.5 alphabetically lists a wide selection of past and present computer systems for printing music.
The large number of periodicals surveyed is due to the interdisciplinary nature of the subject. Computers and the Humanities and Computer Music Journal are the main sources, with a few references to each of numerous other periodicals, including Journal of Music Theory, Perspectives of New Music and Fontes Artis Musicae. Conference proceedings, other review articles and dissertations have also been consulted. A small number of books covering the subjects of music engraving, music notation and manuscript layout, which have been widely referenced elsewhere, are included in the bibliography, as they form a useful foundation for any work on computerized music printing [Donato 1963, Ross 1970, Gamble 1971, Read 1974, Read 1978, Stone 1980, Rastall 1983].
Acquisition covers the process of transferring music into the computer's music representational language. Several different methods of achieving this have been tried, and although it is difficult to divide them into rigid categories, distinctions can be made.
Automatic pattern recognition by optical scanner can be taken as a distinct category. The other methods can be separated into those accessible to anybody with a general knowledge of music notation and those usable only by a musician. For example, use of
an organ keyboard would suggest the latter category. This paradigm can be illustrated diagrammatically :-
Whatever method is used, the aim is assumed to be an encoding which uses an internal music representational language (MRL). In real music acquisition systems various overlaps occur, such as when an organ keyboard is used in conjunction with a graphics tablet [Wittlich 1978a]. This overlap suggests an alternative categorization which involves dividing up the information encoded in a page of printed music into three basic types and associating each with an input device. Thus, pitch may be entered using an organ keyboard, rhythm could be determined by selecting from an on-screen menu of durations using a mouse, and miscellaneous symbols, like slurs, dynamics or text, could be entered using a purpose-built keyboard.
2.2.1 Automatic pattern recognition of printed music
Past and present work on pattern recognition of printed music
is described in detail in chapters 3, 4 and 5. Chapter 3 also provides a discussion of work in the general field of pattern recognition of binary images.
2.2.2 Operator input
There are two musician-only methods which attempt to capture all possible information represented in a score. One uses a directly-connected musical instrument (usually an organ keyboard) while the other involves analysing a soundtrack recording of a performance of the score.
184.108.40.206 Directly-connected instrument
It is impractical to encode all the information represented in a score by sole use of an organ or electronic piano-type keyboard (hereafter organ keyboard), and it would also appear impossible to convert into 100% accurate notation all the information present in an organ keyboard performance [Knowlton 1971, 1972]. A major problem discussed by Raskin [1980a, 1980b] and Clements [1980a] is rhythm-fitting, since no performance contains, throughout, durations which are fully consistent with the notation. Voice assignment has been found to be an intractable problem [Maxwell 1983, 1984] [Byrd 1984]. For example, if two voices out of three in a three-voiced composition are sounding in unison, it is impossible for the system to know whether two or three voices are actually sounding.
Enharmonic notation is another problem of some magnitude. In
tonal music, guidelines might be formulated to assist the machine in determining which particular notation is meant, but for atonal music the problem appears insurmountable [Byrd 1984] [Gomberg 1975, 1977].
Thus, provided the user circumvents the limitations of using an organ keyboard as an input device, it can still form part of a practical system.
220.127.116.11 Soundtrack analysis
Early work in this field by Moorer [1975, 1977] limited input to no more than two voices with further restrictions on the harmonic relationship between simultaneously sounding notes. He stated that 'In general, the system works tolerably well on the restricted class of musical sound'. More recently, Piszczalski and Galler [Piszczalski 1977, 1979, 1981] have, according to Moorer [Byrd 1984, p.78], 'refined monophonic music transcription to a fine art'.
Further work by Chafe , Foster  and others, used artificial intelligence techniques to automatically determine clef, key and time signatures, and enharmonic notation. However, Piszczalski and Galler [Piszczalski 1979, p.203] have asserted that 'the state of the art is nowhere near approaching the successful automatic transcription of polyphonic music recorded on a single track.'
Hence, it can be concluded that recognizing music from a
soundtrack combines all the problems associated with using a directly-connected instrument for input with those involving spectral analysis and psychoacoustics.
18.104.22.168 The compromise solution to the input problem
From the previous discussion it will be realized that, except in very restricted circumstances, methods which appear ideal do have flaws which prohibit their use as sole input devices. Hence, whether a musician or non-musician is entering the music data, the problem becomes one of optimizing the man-machine interface, with any musical ability on the part of the operator serving to speed this interaction. The main types of peripheral device available to any user for entering music data are:- QWERTY keyboard, digitizer (graphics tablet), and pointer (light-pen/mouse/joystick/tracker-ball).
As has been previously stated, the three basic types of information present on a page of printed music (pitch, rhythm and other symbols) tend to associate themselves with particular peripherals, depending to a great extent on the type of music being encoded.
The QWERTY keyboard is always available, which is its main advantage. With suitably defined function keys and/or an overlay together with carefully designed software, the ordinary keyboard can be quite successful, although it is still physically limited by the number of keys. Some systems still rely on the QWERTY keyboard for direct input of alphanumeric music-representational
data, although more use is being made of menu-driven systems with on-screen icons [Hewlett 1988].
The graphics tablet has been separated here from other 'pointing' systems because, where pitch is concerned, it has a unique advantage, i.e., the actual printed score (assuming one exists) can be placed on the tablet (a page at a time) and the noteheads picked out with the pen or stylus, a method successfully used by Wittlich et al, [1977, 1978a]. Hence, this is the only 'pointing' system which uses the score directly. This speeds up entry considerably because it eliminates the repeated movement of the eyes from score to screen. Alternatively, the tablet can be divided up (using an appropriate overlay) into regions, each representing a particular symbol, pitch, etc., so that all aspects of the music may be entered in this way.
The different types of pointer - light-pen, mouse, joystick, tracker-ball - work in a similar way, in that they select symbols from a menu, but vary in their ergonomic convenience. Use of these devices facilitates screen feedback, hence the adoption of abbreviations (e.g., for repeated pattern entry) or short-cutting techniques, such as having various permutations of chord patterns or arpeggio figures available in the menu.
22.214.171.124 Practical assessment of input methods
The following list gives a general view of which peripheral
best suits each category of music information:-
Digitizing tablet (tracing the score with a stylus) i) Organ keyboard (depending on the complexity of the music and the musical ability of the operator)
i) Pointers (+ menu of patterns on screen)
ii) Digitizing tablet (+ menu of patterns)
iii) Organ keyboard (+ metronome click-track)
3) Text, slurs, etc.
i) Pointers or QWERTY keyboard
ii) Digitizing tablet
The order chosen for 2 i/ii and 3 i/ii above is determined by the greater inconvenience involved in moving between score, screen and tablet as opposed to score and screen.
In a test undertaken by the author, the graphics tablet method of entering letter names of pitches has yielded results of approximately 90% accuracy. The opening three lines of the flute part for J. S. Bach's Sonata in C were scanned three times each, with individual lines averaging 48 notes taking about 30 seconds. The results were obtained using a graphics tablet having a resolution of 0.001", i.e., 1,000 points per inch, or approximately 60 points between stavelines.
Taking into account the improvements that could be made to the system used, the results were quite promising. Modifications might include using a cursor with a lens and cross-hair instead of the pen utilized in the test system, plus some form of guidance as to the proximity of the pointer to one of the horizontal pitch lines (i.e., stavelines and centre-lines of spaces) in order to permit re-entry of wayward values. It has to be accepted that in general the stave will not be horizontal and any calculations involving vertical measurements must take this deviation into consideration. Although the bowing of stavelines (mentioned as a problem by Wittlich et al. [1978a]) was not encountered, it must be planned for when indicating the position of the stave (i.e., not only indicating end-points). For a non-musician, a 100-notes-per-minute, 90% accurate system for entering pitch values (letter names only) might form a valuable part of a practical set-up. Wittlich et al. [1978a] cited user-friendliness and speed as the most favourable features of this sort of system.
A deciding factor that emerges here is the type of music involved. For example, the above test was carried out on a sample of Bach, which consisted of more-or-less continuous semiquavers, making entry of the rhythm values particularly easy for a 'mouse and icons' or similar system, with good repeat facilities. In certain cases, however, the pitches also form patterns and this may be an example where a mouse could be used to achieve results faster, picking from a limited set of previously defined patterns, rather than entering all pitches via the graphics tablet or organ keyboard. On the other hand, types of twentieth century music which dispense with the key signature and employ numerous
accidentals could not beneficially be entered using a system where one method is used for entering the letter names of pitches (i.e., organ keyboard or tracing the score on a graphics tablet) and another is used for specifying the desired accidentals. Thus, the choice of method can be seen to be related to both the type of information being encoded (pitch, rhythm or other symbols) and the style of the music.
During the design of Music Representational Languages, much effort has been expended to support abbreviations, for instance to avoid repeated encoding of constant rhythm values or to provide a means of tagging certain patterns (of rhythms or pitches) so that these can easily be recalled. However, this feature must surely be most easily implemented by the software controlling a 'pointer and icons' system rather than the syntax of the M.R.L. (Music Representational Language). The only possible exception to this might be where the QWERTY keyboard is used to enter raw data, where minimizing the number of keystrokes involved in encoding is paramount. In this case, a cursor-key-controlled 'pointer and icons' system may still be faster and will certainly be easier to learn and use [Carter 1984]. As the abbreviated M.R.L. data would almost certainly have to be expanded to the 'long-hand' version at some stage (as in user-DARMS to canonical-DARMS discussed in section 126.96.36.199), program simplification would be achieved by having the user-interface software output standard M.R.L. data. Abbreviations in M.R.L.'s are covered in Section 2.3 - REPRESENTATION. Optimization of the man-machine interface is discussed, for example, by Card, Moran and Newell [Card 1983] in the context of a formal research project, and by Freeman  in
a personal assessment of one particular application (word-processing).
At this point, mention should be made of Armando Dal Molin and his purpose-built music-entry terminals. Dal Molin's significant contribution to computerized music-setting and printing is covered in numerous publications [Dal Molin 1973, 1975, 1976, 1978] [Sargeant 1971]. His Musicomp (PCS 500) terminal [Dal Molin 1978] utilizes a combination of pitch keyboard (i.e. four stacked octaves of white keys) and music-orientated QWERTY keyboard built side-by-side into the console. This permits use of the left hand for Pitch and right hand for Character (symbol) and Spacing, hence the acronym PCS. Good on-screen feedback and editing facilities are significant features of the system, which produces near engraving-quality output on a phototypesetter.
In addition to an input method, a means of internally representing the score is required, as all or part of the information present in the score must be stored electronically. A score can be stored as a graphic image, i.e., as an 'electronic photograph', so that the holding computer has no knowledge of the meaning of the symbols in the image, but this method is of limited practical use. Alternatively, the information contained in the score can be stored using a Music Representational Language (M.R.L.), enabling reconstruction of the score using appropriate software, albeit with inevitable slight differences in layout.
A Music Representational Language is a symbol system, normally using ASCII characters (but sometimes binary or decimal numbers) to represent musical pitches, rhythms or other miscellaneous notational symbols. For example, the letters A to C might represent the pitches of the same names, and the numbers 2, 4 and 8, the durations of a half, quarter and eighth note (minim, crotchet and quaver). Hence, using this simple and restricted M.R.L., the following extract would be written G8 G8 A4 B4 C8 D8 G2.
Obviously, for a useful M.R.L., more symbols would be required to represent octaves, clefs, barlines, rests, dotted notes, slurs, etc. Another factor emerges here, that is, the amount of decision-making which should be built into the score-reconstruction' software, instead of being included in the M.R.L.. For example, in the music extract above, the pairs of quavers are beamed, but this is not indicated in the M.R.L. data; a score reconstruction might appear with separate quavers. Thus, either another symbol could be included, indicating beamed notes, or an automatic beaming facility could be included in the score- reconstruction software. The latter might cause problems, however; for instance it could not be determined automatically how, or even if, a number of notes should be beamed.
Once the score has been converted to M.R.L. data, it can be analysed by software, edited, performed electronically or reconstructed for printing. The hardcopy can be in the form of proofs or finished artwork, consisting of score, separate parts, or piano reduction. Thus, assuming that an M.R.L. data version of a score is desirable, the researcher has the choice of either using an existing M.R.L. or creating his own.
Unfortunately, in the past, music researchers have chosen, for several reasons, to invent their own M.R.L.'s, and continue to do so (see [Gourlay 1986]). In most cases, the M.R.L. was tailored to the particular requirements of an individual research project, and as the nature and scope of projects differed, so did the requirements of an M.R.L.. This variety created the problem which still exists today, i.e., the lack of a standard encoding scheme for representing music scores. The recently established Musical Instrument Digital Interface (M.I.D.I.) standard provides the equivalent for musical sound. The pressing need for a standard has frequently been stressed by authors writing on the subject of computers and music (e.g., [Lincoln 1970b] [Morehen 1979]), but researchers who have encoded large quantities of data using their own particular M.R.L. are understandably averse to re-encoding the information. This has meant that a barrier exists between workers in the field which obstructs the transportation of data and software for analysis, printing etc. Recently, a task group (the Music Information Processing Standards Committee) formed under the auspices of the American National Standards Institute has been asked to propose a standard for the interchange of musical
information. It is intended to use only printable characters as an extension of SGML (Standardized General Markup Language), the code which covers production aspects of text publication. The principal document produced by the committee includes an outline for the standard [MIPS 1988]. Also, a working group of the Music Library Association is currently examining the possibility of using encodings of music in library cataloguing [Hewlett 1986b].
Irrespective of whether the researcher is choosing an existing one or creating his own, various attributes of an M.R.L. have to be assessed; in particular the scope (i.e., completeness), structure, (hierarchical or sequential), and efficiency (i.e., compactness). Also to be considered are the use of mnemonics, number of passes, availability of software for syntax/semantic checking or translating, existence of a shorthand version, and compatibility with existing facilities.
2.3.1 Existing M.R.L.'s
Much of the literature on computers applied to music relates to the subject of particular M.R.L.'s [Heckmann 1967] [Brook 1970a] [Lincoln 1970a]. However, as few as six have been used in significant research, or have been specified thoroughly enough for practical use. A comprehensive survey of M.R.L.'s has been produced by Boody , together with a more detailed analysis of six of these which met his list of criteria deemed necessary - but not sufficient - for a useful language. From consideration of these evaluations, three M.R.L.'s emerge as the most suitable for general use, with a definite ranking of DARMS, MUSTRAN, ALMA.
188.8.131.52 DARMS: Digital Alternate Representation of Musical Scores
A large proportion of the literature on computers applied to music mentions DARMS at some point. Originating in the 1960's, the DARMS Project has involved work by Stefan Bauer-Mengelberg (the M.R.L. itself), Raymond Erickson (Syntax-checker), Anthony Wolff and Bruce McLean (user-DARMS to Canonical-DARMS translater, [McLean 1980]), David Gomberg (score-layout programs) and Melvin Ferentz (production of printed score). There are three main papers [Bauer-Mengeiberg 1970] [Erickson 1975, 1983] which discuss DARMS in detail as well as three publications [Gomberg 1975, 1977] [Wolff 1977] covering aspects of representation and music-setting which form part of the DARMS project, with its aim of producing publication-quality music from DARMS data (See also [Gomberg 1972] [Wolff 1972] [Feldman 1973] [Bauer-Mengelberg 1972, 1974a, 1974b] [Erickson 1977]). A user manual has also been produced [Erickson 1976].
DARMS was specifically designed [Erickson 1983 p.176] 'to capture accurately all the information provided by the composer, but not those details of layout within the province of the engraver or autographer.' DARMS has become the most widely used M.R.L. because it can be used to encode most music published since c.1600 which uses Common Musical Notation (C.M.N.).
The encoder can make use of extensive abbreviations which are permitted in user-DARMS but these are expanded by the Canonizer software into their complete version, known as
'Canonical-DARMS'. Hence, there may be several versions of a score in user-DARMS, but there will be only one Canonical-DARMS representation. Briefly, the representation uses numbers for pitches (21 to 29 cover lines and spaces on the stave), letters for rhythm-values (Q, E, S, etc Quarter, Eighth and Sixteenth notes respectively, i.e. crotchet, quaver and semiquaver) and other ASCII characters for miscellaneous symbols, e.g.:(# ,-, *) =
respectively. Chords and polyphonic music are catered for, the latter by a method called Linear Decomposition Mode, i.e., encoding one voice per pass over the score.
184.108.40.206 MUSTRAN: Music Translater
MUSTRAN [Wenker 1969, 1970, 1972a] was developed by Jerome Wenker, originally for ethnomusicological purposes, but the revised version, MUSTRAN II [Wenker 1972b, 1974, 1977] includes more 'art-music' notation, representing C.M.N. almost as comprehensively as DARMS.
MUSTRAN (II) uses more mnemonic symbols than DARMS and has better software support (translator and utilities). The Indiana University Computer Music System [Wittlich 1978b], which incorporates Donald Byrd's SMUT (System for Music Transcription) software [Byrd 1984] uses MUSTRAN as its Representational Language. It was chosen because of its mnemonic code, relative completeness and existing translator and syntax analyser. Both the original MUSTRAN and MUSTRAN II have been described in detail by Wenker [see Wenker 1969 to 1977] while details of the numerous MUSTRAN utility programs now available at Indiana University can
be found in [Hewlett 1985].
220.127.116.11 ALMA: Alphanumeric Language for Music Analysis
ALMA [Gould 1970], which can cope with most C.M.N. (including polyphony), evolved from the 'Plaine and Easie Code' [Brook 1964, 1965, 1970b] invented by Barry S. Brook and Murray Gould, which while sometimes used (see [Rösing 1985]), is limited to monophonic music representation. ALMA supports abbreviations, optional multi-pass encoding, user-determined order of encoding and user-defined representational symbols. ALMA also supports a novel feature which helps with encoding repetitions, i.e., cyclic duration definition. This means that a recurring rhythmic pattern can be encoded once only and it will automatically be cyclically applied to following groups of the same number of notes.
A common problem with both MUSTRAN and ALMA is the use of letters to represent pitches, for although this seems appropriate at first (being suitably mnemonic), it means that a separate octave indicator has to be used. For example, in ALMA, the apostrophe (') is used once for each octave above middle C and commas (,) correspondingly indicate octaves below middle C. Thus, a passage of music which alternates across the boundary between two octaves will, when encoded, consist of numerous commas or apostrophes compared to the number of actual pitch symbols. This inefficiency is overcome in ALMA by an abbreviation facility which allows the encoder to indicate only a change of octave relative to the present one (+ or - a fourth relative to the present note). Obviously, this problem does not occur in DARMS, with its numeric
2.3.2 M.R.L. structure
The structure of the M.R.L. is for the most part determined by the method of encoding polyphonic music. Various ways of referencing the notes in multi-part music have been adopted or proposed (e.g., [Clements 1980a, 1980b] [Maxwell 1983, 1984]).
One method is to encode voices separately with a tag of some sort to indicate which is which, but this can be wasteful if a composition consists almost entirely of one voice with just a few chords, since the subsidiary voices will have to be encoded throughout. Alternatively, encoding can be orientated around vertical 'time slots', so that all notes occurring simultaneously may be referenced together. Different voices then 'switch in and out' as and when they are required. Both Clements and Maxwell have favoured the latter approach, defining everything in the time domain, because the system thereby avoids any constrictions which would arise through the use of a musical hierarchy. Clements [1980a] also describes a 'neutral' M.R.L. implemented at the University of Western Ontario, which contains enough information in its data to facilitate ready conversion to either a 'sound output file' (for performance) or DARMS format (for printing).
2.3.3 The Editor
The minimum features of an editor have been formalized by Clements [1980a], as have the varieties of operational scope
-22-needed [Buxton 1980, 1981]. Basically, the editor requires a data pointer, together with the following functions, the operation of which should be self-evident: delete, insert, change, transfer, search, substitute and transpose. The five categories of scope defined are: simple, block of time, local attributes, contextual attributes and named structural entities. In order, these refer to single note or entire score, notes within a certain time interval, notes encompassed within limits of pitch and duration, a note or notes within a certain musical context, and notes of a defined motif or theme.
Various arguments have been put forward supporting different structures for M.R.L.'s; when consideration is given to the incorporation of an editor into the system, however, opinions [Maxwell 1984] [Clements 1980a] come down in favour of a sequential, time-ordered structure. This facilitates access to the data by the editor because information which is close together in the notated score will also be close in the Music Representational Language form.
It should be stressed that when entering information, the user can be buffered from the raw M.R.L. data by. the use of certain types of user-interface, as described in sections 18.104.22.168 and 22.214.171.124. Hence, different assessment criteria must be applied to M.R.L.'s when data is input via a QWERTY keyboard, compared to, say, a mouse and icons system. When using the former, as has been stated previously, minimizing the number of keystrokes is of paramount importance, so abbreviations (shorthand) and mnemonics (for ease of use) would be prime factors for consideration.
If another means of input is being employed, however, e.g., organ keyboard or graphics tablet, then comprehensiveness and efficiency are perhaps the most relevant features to be considered.
The issue of translation seems to be gaining in importance at present, as researchers accept the fact that there is no standard method of representing printed music, and opt for encoding data in as crude a form as possible so that it can then be translated into whichever M.R.L. is later required. If only pitches and rhythms are required initially (perhaps so that some form of analysis can be undertaken), and then later printed scores are required and only DARMS-compatible printing software is available, then it should be reasonably easy to convert the encoded data into the DARMS format and at the same time add previously omitted information. However, despite solving the problem of researchers' tenacious defence of their own M.R.L.'s (i.e., this approach allows them to retain their own data format), the result is a proliferation of translation software.
2.3.4 Problems concerning score representation in the context of printing
One example of this has already been mentioned, i.e., whether to indicate beaming in the M.R.L. or to try to formalize the rules for beaming of notes and to incorporate this knowledge in the score-reconstruction software. To take another example, the slur
is 'attached' to the two notes when included in the M.R.L. data, but its exact position and curvature will probably be determined by the music-setting software. Some M.R.L.'s do, however, make provision for stem direction (for example) to be encoded (e.g., U and D for up and down stem respectively) if desired.
A detailed discussion of some of the problems involved in representing all the complexities of music notation can be found in Wolff . For example, sometimes too many notes are present in a bar, either because the notes are an appoggiatura written in small notation or because a triplet sign has been omitted. These features have to be indicated in some way to prevent syntax-checking software producing an error. Another problem relates to horizontal positioning, where notes to be sounded simultaneously are of a similar pitch and must be separated out horizontally; this separation can also lead to 'too many notes in a bar' as well as variations in layout.
In coping with the above cases there is a trade-off between the interpretative ability of the encoder, the knowledge-based rules programmed into the score-reconstruction software and the graphical information included in the M.R.L.. Donald Byrd [Byrd 1984] asserts that fully-automatic reconstruction of high-quality music notation is not possible without artificially intelligent
software for this purpose. As this is not available at present, a compromise has to be reached; hence the trade-off mentioned above.
Most of the problems concerned with score-representation seem to be caused by the transfer from two dimensions (pitch and time) to the single-dimensional string of ASCII characters. These difficulties are compounded by the fact that there is not always a one-to-one correspondence between music-notational symbol and ASCII character(s). This is due to the graphical variations which can occur in some musical symbols (e.g., slurs).
It is the actual hardware used which has the most influence on reconstruction. Once the master copy of the printed page has been produced, it can be mass produced by traditional means, such as offset lithography. The software of a music printing system can be designed to be device-independent, at least within certain categories of printer. It is easier, however, to convert from a vector-image (or random-scan) construction scheme to a raster-scan format than vice versa. Vector-drawing image construction means building up the image by drawing line segments (vectors); raster-scan implies plotting a large number of points while making horizontal sweeps over the imaging area. In the former case, small segments may not be drawn accurately and producing dots can prove to be a problem, whereas with the latter it is the number of points per unit area (i.e., the resolution) which is crucial to producing a good image (which appears not to be made up of
Numerous types of printer are available for producing hardcopy computer output. Music printing systems have tended in the past to use three main varieties, the dot-matrix printer, plotter and phototypesetter. The primary features which determine these choices are price, resolution and speed. The printers' best attributes are shown by category in the following table. The phototypesetter, for example, provides the best resolution and speed at the worst (= highest) price.
price resolution speed dot-matrix 1 3 2 plotter 2 2 3 phototypesetter 3 1 1
The dot-matrix printer is widely available and very popular because of its price and versatility. It can produce scores at a resolution of up to approximately 360 dots per inch (d.p.i.) which is adequate, although beams which slope only slightly will appear as a 'staircase' and slurs will not be smooth. These disadvantages can be minimized by producing oversized originals and then using photoreduction at the production stage. More often, though, the intention is to use the dot-matrix printer for producing draft copies for proof-reading or one-off prints for use in an educational situation or by a composer. Often the dots which constitute the image are large compared to the 'grid' on which they can be positioned, so that adjacent dots overlap and, for
example, a line two dots wide would be less than twice as wide as a line of single dot thickness.
In the past, the plotter has been by far the most widely used output device for computer printing of music within the context of research projects (see section 2.5). Its two main forms are the X-Y flat-bed pen plotter and the drum plotter. In the former, the pen travels over both axes, whereas with the latter the pen moves over one axis only and the paper moves over the other. Although the plotter is relatively slow, it can resolve up to a thousandth of an inch, but then suffers from a problem similar to the dot-matrix printer in that the ultimate resolution is decided by the pen being used, and not by the 'grid' upon which it is positioned. Again, photoreduction can be used to improve the perceived resolution and assist in eliminating 'staircase' effects.
The phototypesetter also exists in two forms: mechanical and digital [Seybold 1983], but the latter is rapidly taking over from the former. Both types produce output on film but the mechanical typesetter uses templates and an optical system to produce very high quality images with an accuracy in the region of +/- one thousandth of an inch. The use of templates dictates that the character-set is built into the hardware. This restricts the number of symbols to less than that needed to cover all orientations of beams and slurs, and is less flexible than the digital approach. In a digital typesetter, the number of characters/symbols available is limited solely by the on-line storage capacity. So, although the digital typesetter is the more
expensive variety (tens of thousands of pounds), it has enormous flexibility and is able to produce images of very high quality (approx. 2500 d.p.i.) making it the ideal music printing device.
More recently, other designs of printer have been developed and refined and hence have become available for music printing [Weber 1986a, 1986b]. Specifically, these are varieties of non-impact machines, such as thermal transfer, electro-erosion, electrostatic and xerographic printers.
Thermal transfer printers are capable of approximately 300 d.p.i., an example being the IBM Quietwriter 7 typewriter/printer, but the short life-span of the ribbons used leads to high running costs.
Electro-erosion printers (such as the IBM 4250) produce up to 600 d.p.i. (low typeset quality) by using a high-density printhead to burn away the metallic surface covering a black backing paper, which is then used to produce final output on film.
Electrostatic printers produce a resolution of up to 400d.p.i. Their print quality and contrast, however, are not as good as the xerographic printers described below. A disadvantage of electrostatic printers is their requirement of special paper.
Of all xerographic (or electrographic) printers, the laser printer is, at present, the most popular form. It is being used widely for music printing (see section 2.5) where it is seen to benefit from some of the advantages of the phototypesetter (high
speed and resolution) but with none of the disadvantages of the plotter and dot-matrix printer. Other varieties of xerographic printer use a different light source such as light-emitting diodes, or a liquid crystal shutter to control the light. Working on principles similar to those of a photocopier, the modulated light source directed onto a rotating drum produces an image on the charged drum surface. This is then used to transfer toner onto the paper, where it is heat-fused. A diode or liquid crystal shutter as the light source or controller, respectively, gives the printer greater reliability because it cuts down on moving parts. Speeds for laser printers vary between six and 200+ A4-size pages per minute, prices are from £1,000 upwards, and maximum resolution is about 600 d.p.i.. Duplex printing (i.e. on both sides of the page) and A3 paper-handling - both important features for music printing - are now becoming available in cheaper machines.
Normally, assuming a laser printer (or similar) has the facility to address all points over its imaging area, the information actually transmitted over the interface between host computer and printer is a coded description of the original image. This produces significant data compression compared to transmitting a complete bit-map representation. A raster image processor (R.I.P.), normally contained in the printer, converts the transmitted code into a raster image and controls the marking engine itself. It is the R.I.P.'s own command language which determines the text/graphic printing capabilities of any particular printer. There is a similarity between the laser printer and phototypesetter in that, in both cases, the host computer has merely to transmit information regarding which symbol
(character) is to be printed, where on the page, and perhaps in what orientation. The printer can then construct the bit-map form of the image and thus offload a large amount of work from the main computer. Currently, the effective standard for this type of coded data transfer between computers and printers is Adobe Systems' 'Postscript', although other page description languages (PDL's) are in use, for example Xerox's Interpress. In practice, this means that the same data can be sent to an appropriate laser printer or phototypesetter, and the only difference in the output image will be the change in resolution. Also, 'Display Postscript' is now becoming available, providing even more device-independence, by enabling a Postscript encoded image to be displayed on-screen.
The following table can be viewed as an enlarged version of the survey given in Donald Byrd's thesis 'Music Notation by Computer' [Byrd 1984]. References have been added pertaining to systems which Byrd mentions. Information on systems which were recent at the time of his writing, has been expanded upon, and details of some new systems have been added. Also, the information is presented in a clear tabular form. Ideally, the same features of each system would have been examined to facilitate direct comparison; the systems vary so much, however, that this is not possible, especially considering the varying amount and age of information which is available. Examples of output from significant systems are to be found in [Clements 1980a] and [Hewlett 1985, 1986b, 1987, 1988]. Where the information provided
is based on [Byrd 1984], the subjective descriptions of output (e.g., 'high-quality' scores) have been retained and where the current author's opinion is being expressed, a similar scale has been adopted, i.e., low or poor, adequate, reasonable, high, very high or very good, excellent or engraving-quality.
As the price of technology falls, significant developments are occurring at a rapid pace. For example, the hardware used in the Mockingbird system developed at Xerox's Palo Alto Research Center, deemed 'prohibitively expensive' in 1984, may in the not-so-distant future come within reach of most music publishers' budgets, if not those of music copyists. More music printing software is becoming available for popular microcomputers, which is having a significant impact, especially where the Postscript page description language is used, with its aforementioned flexibility. The possibility of proofing output on a laser printer and then using a bureau service to produce final typeset material from the same data is proving attractive in music production (as well as general graphics applications) because, while giving access to top-quality output, it removes the need to invest heavily in typesetting equipment.
TABLE OF MUSIC PRINTING SYSTEMS Name of system Instigator(s) References AMADEUS Kurt Maas [Maas 1985] Amadeus uses polyphonic real-time input by organ keyboard -32-
and/or QWERTY keyboard. Facilities for playback and transposition are available, and editing is very versatile giving varied layouts, including text. The system is MIDI-compatible, and, connected to a laser phototypesetter, gives excellent quality. The notational vocabulary is comprehensive and layout facilities cover several parts to a stave and parts crossing from one stave to another. The system is used by its originators to provide a music-setting service (used, for example, by Schotts).
C.C.A.R.H. System Walter B. Hewlett [Hewlett 1985, 1986a, 1986b, 1987, 1988] [Selfridge-Field 1986b]
The system of the Center for Computer-Assisted Research in the Humanities runs on the Hewlett Packard 1000 computer using the IBYCUS operating system. Input is by organ keyboard (each voice separately) with a playback facility (via any MIDI-compatible synthesizer) available. Draft-quality output is by dot-matrix printer, although a limited Hewlett Packard Laser Jet printing option is available. The system is aimed at the creation of a music database (initially the works of Bach and experimentally those of Corelli, Legrenzi and Handel) for musicological and educational purposes.
COMPOSER'S ASSISTANT Syntauri Corporation [Aikin 1983] Composer's Assistant uses real-time input via a synthesizer to an Apple II computer, with output by dot-matrix printer. -33-
Facilities available are very limited, especially editing.
FINALE Coda Software [Hewlett 1988] [Finale 1988]
Finale is a software package for the Macintosh with multi-channel real-time MIDI input using 'Hyperscribe' which has a unique facility for coping with tempo changes. Other input options include QWERTY keyboard, mouse and non-real-time MIDI. A wide variety of symbols and score formats are available, as are user-definable symbols and text underlay. Part extraction and playback via MIDI are also possible. Output is to any Postscript device and a version of the program for the IBM PC is under development.
H B MUSIC ENGRAVER H B Imaging Inc. [HBEngraver 1988a, 1988b]
H B Engraver is a software package for the Macintosh which automatically positions musical symbols and text according to a user-definable spacing 'ruler'. Alternatively, symbols can be positioned manually. It is available in a version for composers/arrangers and also in a special publishers' edition. Input is achieved by use of the mouse and output is via any Postscript device using the 'Sonata' font (the proprietary 'Interlude' font is also available). Multiple voices per stave, chords, various markings and a range of formats are available.
-34- INTERACTIVE MUSIC SYSTEM Lippold and Dorothea Haken (C.E.R.L.-Illinois) [Schmid 1984][Scaletti 1985] [Hewlett 1985, 1986, 1987]
Based on the PLATO computer system (using the C' programming language), the Interactive Music System is part of the computer-based music education system at the University of Illinois. Input is via an organ keyboard with alphanumeric and graphic editing and playback facilities available. Up to 60-part scores can be produced, with a wide range of notational symbols (including n-tuplets) available. Draft-quality output is provided by a dot-matrix printer and laser printer output is available via an Apple Laserwriter.
LA MA DE GUIDO Llorenç Balsach [Balsach 1986][Guido 1988]
La Ma De Guido, a software package for the IBM PC, is used by its originators to provide a music-setting service. Input is by QWERTY keyboard or MIDI synthesizer and output is via a plotter. Flexible editing and user-defined symbols are available, as is transposition and the facility to produce parts from a score. A limited version restricted to four voices and two staves per system is also available, as are test programs for either package. A separate score performance module permits playback of up to eight voices via a MIDI synthesizer, with control over tempo and other parameters.
-35- LUDWIG William Reeves and William Buxton (et al.) [Reeves 1978][Buxton 1978a, 1978b, 1979]
Ludwig is a score-editing system developed as part of the University of Toronto's Structured Sound Synthesis Project (SSSP).
MANUSCRIPT Rebecca Mercuri [Mercuri 1981]
Manuscript is a music notation system for the Apple II using menu-input and editing.
McLEYVIER David McLey (SYNTRONICS) [McLeyvier 1982][Gilbert 1982][Spiegel 1983][Hewlett 1987]
The McLeyvier uses input via organ keyboard (either real or non-real time) or M.R.L., with other features similar to the Synclavier. The system is now owned by Syntronics of Toronto.
MOCKINGBIRD John Turner Maxwell III & Severo M. Ornstein (Xerox PARC) [Roads '81] [Maxwell 1982, 1983, 1984] [Ellis 1984] [Hewlett 1986b]
Mockingbird uses real-time input via Yamaha CP3O keyboard (piano music only) with powerful editing facilities to convert
piano-roll notation to C.M.N. using menus and a mouse. Mockingbird runs on the Xerox Dorado (Xerox 1132) in Mesa and produces very good quality output via a laser printer. A playback facility is incorporated.
MP-1 MINIPRINTER Yamaha Inc. [Yamaha 1983]
The MP-l is a synthesizer with built-in pen plotter (using 2 1/2" wide paper) which prints melody lines only (i.e. monophonic).
MPL - NOTATE Gary Nelson [Nelson 1973a, 1977]
MPL - NOTATE is part of an integrated suite of music programs (MPL Music Program Library) written in APL on a Xerox Sigma 9. Input is by QWERTY keyboard with plotter output of fairly high quality scores, but with only one voice per stave.
M S / SCORE Leland Smith, Passport Designs Inc. [Smith 1973,1979][Bowles 1974][Hewlett 1985, 1986b][SCORE 1988]
M S / SCORE is a well-known system using the researcher's own encoding language to produce multiple voices per stave. Feedback and interaction are essential features, permitting the system to cope with music of unlimited complexity. The use of vector graphics permits output via nine or 24-pin dot-matrix printers or any Postscript device, including the Apple Laserwriter and
appropriate phototypesetters. A wide variety of symbols, good automatic beaming, automatic page layout and production of parts from a score are all available. Unusual kinds of notation such as neumes, mensural notation and lute-tablature can also be produced, as can user-designed symbols. SCORE, the commercially-available version of the software, runs on IBM PCs.
MUPLOT A. James Gabura [Gabura 1967a, 1967b]
MUPLOT uses alphanumeric input on the IBM scientific computer, producing single-voice-per-stave scores of high-quality on a plotter, but with severe limitations.
MUSCOR II Charles Render [Render 1981]
MUSCOR II uses the researcher's own encoding language but details as to the extent of the implementation of the system are unclear.
MUSECOM II Jim Troxel [Musecom 1977][Price 1977] [Wittlich 1978b]
Musecom II consists of a single console which contains an organ keyboard for input (in real-time), a plotter for output (using pre-drawn manuscript paper) and a monitor screen. The latter permits editing of up to 20 lines of music. A playback facility is available.
-38- MUSIC EDITOR/LAFFANGRAF John Laffan [Hewlett 1985][Laffangraf 1985]
Music Editor runs on the IBM PC with up to six staves on-screen (in three possible sizes) but more staves are possible in total. Cursor keys are used to input pitch, with a QWERTY keyboard (and M.R.L.) used for all other information, but there is an organ keyboard option. Chords are possible and beaming is automatic, but the variety of symbols is limited. Output is by dot-matrix printer, giving quality which is adequate, but better on large music notation (e.g., piano scores) rather than orchestral scores. Limitations include problems with spacing and beams. Facilities available include good editing, transposition and parts from scores.
MUSIC PROCESSOR Etienne Darbellay [Hewlett 1985]
The Music Processor is a system orientated towards musicology which runs on the Texas Instruments Professional Computer and IBM PCs. Defined function keys are used for input with up to nine staves on-screen and automatic spacing as a default. Special notations (including mensural notation) are available, as are editing facilities and dot-matrix printing.
MUSIC PUBLISHER Graphic Notes, Trevor Richards [Hewlett 1988][Music Publisher 1988]
Music Publisher is a software package for the Macintosh, based on the work of Trevor Richards. It uses a separate 'PRESTO
pad', in addition to mouse and QWERTY keyboard, for input. Output is via any Postscript device or the Apple Imagewriter. A MIDI playback facility is available and an option for MIDI input is under development. A wide range of symbols and score formats are available together with the proprietary 'Repertoire' font. A dictionary of musical expressions is included for spell-checking.
MUSICOMP (PCS 500) Armando Dal Molin [Dal Molin 1973, 1975, 1976, 1978] [Sargeant 1971] [Selfridge-Field 1986a] [Hewlett 1988]
The Musicomp uses custom-built hardware, including four stacked octaves of 'pitch keys' and a music-orientated alphanumeric keyboard, for input. It forms a commercial system with good feedback and editing facilities producing near-engraving quality output on a phototypesetter (as of 1982, hand-finished). Publishers Belwyn Mills currently use four Musicomp terminals. A version for the IBM PC using an auxiliary keypad for pitch input is under development.
MUSICSYS/3600 Bernard S Greenberg and Douglas Dodds (Symbolics Inc.) [Hewlett 1985]
Musicsys is a system running on a Symbolics 3600 computer using QWERTY keyboard for input of researchers' own M.R.L.. Playback of up to six voices is available internally and
interfacing to a MIDI synthesizer is also possible. A mouse editing facility was under development as of 1985 and a laser printing facility is already available.
MUSIGRAPH William A. Watkins [Watkins 1984][Selfridge-Field 1986b][Hewlett 1987]
Musigraph is a commercial system which runs on TRS-80 computers, interactively handling complex material. It produces excellent quality output on a phototypesetter, together with some manual additions. In 1984 it was being used to provide a music-setting service to major music and book publishers in North America, but this operation has since been dissolved and the system taken over by Grawemeyer Industries of Kentucky.
NEDIT Dean Walraff [Walraff 1978]
NEDIT is a system developed at M.I.T. which uses organ keyboard input in non-real time.
OXFORD MUSIC PROCESSOR Richard Vendome [Vendome 1986]
O.M.P., a software package for the IBM PC, which was undergoing beta-testing during 1988, uses QWERTY keyboard input of M.R.L. data and plotter output (alternatively a dot-matrix printer can be used for proofing). A utility to convert Hewlett Packard Graphics Language (HPGL) data into Postscript is provided to
enable printing via a suitable laser printer or phototypesetter. Multiple voices per stave are possible and a limited range of symbols are available. The quality of output is, after photoreduction, equal to engraving.
PERSONAL COMPOSER Jim Miller [Freff 1983][Hewlett 1987]
Personal Composer is a software package running on the IBM PC, using a MIDI-compatible synthesizer for real-time input and a dot-matrix printer or laser printer with the 'Sonata' font for output. It is a highly interactive system using a mouse and menus or, alternatively, QWERTY keyboard editing. Part extraction, transposition and MIDI playback are available, and text can be included in scores. Rhythm verification is undertaken automatically.
PROFESSIONAL COMPOSER Mark of the Unicorn Inc. [Moody 1985][Yavelow 1985][Hewlett 1986b]
Professional Composer is a software package for the Apple Macintosh, permitting up to 40-stave scores, with a large variety of symbols available. Pitch entry is by on-screen cursor, while other symbols are selected from on-screen menus. Editing is by cut-and-paste, so that text and metronome markings, etc., can be freely added. A transposition facility is available. Chords can be used, but different durations are not permitted simultaneously on
one stave. Main beats are automatically aligned, but barlines must be entered by hand. Beams are available (including n-tuplets) but these are always horizontal, presumably because of the dot-matrix printer originally intended as the output device (although the Apple Laserwriter can also be used). A preview facility gives a reduced view of the page as it will appear on the printer. The program is currently being used by Garland Press in the production of editions of 16th-Century music.
SCAN-NOTE Mogens Kjaer (Dataland Co.) [Dataland 1979] [Orsted 1976]
(Superseded by 'Toppan Scan-Note - see entry below)
Scan-note used three keyboards for input (organ in non-real time, QWERTY, and dedicated symbol keyboard). Output was via a plotter (double size), with hand additions, covering moderately complex material. The quality was nearly up to engraving standard. A transposition facility was available. Originally, this was a commercial system.
SCOREWRITER Con Brio Digital Synthesizer [Con Brio 1982][Ellis 1984]
(Superseded by 'Toppan Scan-Note - see entry below)
Scorewriter uses a synthesizer as input device in conjunction with 'Music Programmer' software which permits editing of a keyboard performance by interacting with a conventional music score displayed on a built-in monitor screen. Printout is via a dot-matrix printer.
-43- SMUT (+MUSTRAN) Donald Byrd [Byrd 1970, 1971 1972, 1974, 1976, 1977, 1980, 1984][Hewlett 1986b, 1987, 1988]
Input to SMUT is via M.R.L. (MUSTRAN) or organ keyboard (in conjunction with a translation program). High-quality output is produced on a plotter, although the software is designed to be independent of output device. Important features of the system include portability and routines for rhythm clarification and automatic beaming. SMUT allows one or two voices per stave and multiple staves. The software is currently being adapted to run on the Macintosh using Adobe Systems' 'Sonata' music font (a library of approximately 200 symbols) under the product name Nightingale.
SOUNDCHASER NOTEWRITER/POLYWRITER Passport Designs Inc [Soundchaser 1982, 1984][Ellis 1984]
Polywriter uses real-time organ keyboard (MIDI-compatible) input, played along with a click-track, giving resolution to triplet semiquavers. Eight score formats are available (from single stave to 40-part orchestral scores) with a 2700 notes-per-page capacity. Fully polyphonic notation is allowed, including ties, beams, split stems, double-sharps and flats and 8va, plus 40 automatic instrument transpositions. Up to 28 individual polyphonic parts can be recorded, with fairly comprehensive editing facilities, including adding text. The software runs on Apple computers with the Soundchaser keyboard (or similar MIDI-compatible) and produces adequate output on a
dot-matrix printer. Notewriter was a monophonic predecessor.
STAVEWRITER Fairlight Corp. [Ellis 1984]
Stavewriter is a software package for the Fairlight Computer Music Instrument which allows high-quality printing of music from either real-time performance or a dedicated M.R.L.. As of 1984, only monophonic C.M.N. was possible (later four parts were to be available), or all eight parts of real-time input could be printed in 'simplified notation'. Options available include adjustable stave proportions and positioning, proportional spacing, transposition and automatic calculation of irregular rhythmic groups. The system is tailored to a specific plotter (the H.P. 7475A), which produces very good output, although the proportions of some symbols are not quite correct and spacing is abnormal in some cases.
SYNCLAVIER MUSIC PRINTING OPTION New England Digital Corp. [Synclavier 1983][Ellis 1984][Talbot 1988]
The Music Printing Option for the Synclavier uses either synthesizer or dedicated M.R.L. ('SCRIPT') input, with output of high quality by laser printer or phototypesetter (optionally by dot-matrix printer). One or two voices per stave (including chords) are available, as is feedback, but editing possibilities are limited. Notational vocabulary includes n-tuplets, dynamics, articulation marks, instrument names, text and page or bar numbers. The system is currently undergoing substantial revision
THEME - THE MUSIC EDITOR Mark Lambert [Lambert 1983][Hewlett 1987, 1988]
THEME is a system for use in musicological applications as well as printing/editing, etc. It handles up to 16 polyphonic voices and eight notes per stem, using QWERTY keyboard cursor-control input. Beams and stem-direction are produced automatically and a wide variety of notation is available. Ornamental passages can be freely inserted while maintaining vertical alignment in the printed score. The software runs on the Apple II, TRS-80, or IBM PC producing adequate quality output from a plotter, dot-matrix or laser printer. As of 1983, the facility to produce parts from a score was mentioned as being under development. Sound playback is possible via a MIDI synthesizer.
TOPPAN SCAN-NOTE Toppan Printing Co. [Toppan 1984, 1988][Hewlett 1986b]
The Scan-Note system described above was taken over by the Japanese printing company Toppan Ltd. and became the Toppan Scan-note system. Input as above. Output is via dot-matrix printer for proof-reading (enabling error-correction and adding of instrument names, dynamics etc., using a graphics terminal), and laser-typesetter for engraving-quality final copy. Facilities available include parts from a score, transposition, alterable layout and format. Available examples are conservative, so it is
difficult to assess the versatility of the system as regards quintuplets, septuplets, appoggiaturas, etc. Although multiple staves (single line per stave plus chords) are possible, there is no evidence of multiple voices on one stave. The system is in use commercially (for example, by Bärenreiter Verlag), but is also available running on the Apple Macintosh II.
Norbert Böker-Heil [Böker-Heil 1972]
A system which uses ALMA input and plotter output in producing single-voice-per-stave scores of good quality.
Donald Cantor [Cantor 1971]
This is early work, based on that of W.B. Barker, limited to two voices on two staves using menu-entry and running on a PDP-ll computer and four cathode ray tubes. The system has a playback facility.
A-R Editions Inc. [A-R Editions 1985][Hewlett 1986b]
A-R Editions' system is part of a commercial operation, producing engraving-quality output from a phototypesetter, using QWERTY keyboard input of a dedicated M.R.L. (a hybrid of FASTCODE - developed by Thomas Hall at Princeton University - and DARMS). The software checks syntax and does automatic formatting, positioning of stems, beams, slurs, etc. Automatic extraction of parts from a score is possible. It is hoped that a large databank
of encoded music can be created. The only examples available show no evidence of a multiple-voices-per-stave capability. The system is used both for A-R Editions' own publications and by other music publishers.
Lejaren Hiller [Hiller 1965]
This is early work on the setting of music using an ILLIAC I computer and Musicwriter typewriter for input and output, producing high-quality, single-voice-per-stave scores, but limited in many ways.
Prentiss Knowlton [Knowlton 1971, 1972]
This system uses both types of keyboard for input of pitch and rhythm (real-time), i.e., an electronic organ linked to PDP-8 computer, producing limited output of poor quality.
(for M.I.T. LISP machine) William Kornfeld [Kornfeld 1980]
This system uses M.R.L. input or real/non-real time input by organ keyboard with good editing made possible using a mouse but on a bit-map representation (i.e., in image space).
Harry Lincoln [Lincoln 1970a]
This system uses DARMS input and produces low-quality output consisting of limited complexity music on a line printer
with a music character print chain.
Gary Wittlich (et al.) [Wittlich 1973a, 1973b, 1977, 1978a, 1978b]
This system uses real-time organ keyboard and graphics tablet for input but the only output samples available are of poor quality.