ï~~
TIME MANAGEMENT IN INTERACTIVE SCORE EDITING
Przemyslaw Prusinkiewicz
Department of Computer Science
University of Regina
Regina, Saskatchewan, Canada
ABSTRACT
Problems related to interactive score editing are surveyed. Four aspects of editing: the editing operations,
time control, sound synthesis control and score viewing
are distinguished. The time factor, perceived as the distinctive feature differentiating score editors from text
editors, is given particular consideration. General discussion is illustrated with examples based on the design
of an interactive score editor for microcomputers, called
INTERSCORE
RESUMS
Cet article prisente une analyse des probldmes lids a
l'idition musicale interactive. Quatre aspects de l'idition
y sont discutis: les opdrations d'ddition, le controle du
temps, le contr8le de la synthise du son et la
reprisentation visuelle de la musique. On attache une
attention toute particulidre au facteur temps, percu
comme attribut characteristique de l'dition musicale
l'opposant a l'dition du texte. La prdsentation gdndrale
est iInustrie aver des examples fondds sur
1'INTERSCORE - un 6diteur destine particulidrement
aux microordinateurs.
1. INTRODUCTION
In computer music, a score can be specified either as a
program or as a data file. In the first case the score is a
sequence of statements in a sound synthesis language,
for example Music V. The process of score specification
is similar to computer programming in other languages.
In contrast, if the score is perceived as a data file, its
preparation is similar to text editing. In this case, a text
file is created on a virtual strip of a paper of potentially
indefinite length. A user can view a selected portion of
the file on the screen. In WYSIWYG (What-You-SeeIs-What-You-Get) editors, special consideration is given
to make the image on the screen similar as possible to
the paper copy of the edited document. Consequently,
at any moment the user can completely evaluate all
aspects of his work. This feature is an essential element
of the man-machine interaction while editing.
Maintaining a comparable level of interaction in musical score editing is by far more complicated then in text
editing, because a score is not a static text or picture,
but a sequence of events in time. Hence, a fully interactive WYEWYG" (What-You-Hear-Is-What-You-Get)
editor must provide real-time acoustic feedback. This
can be achieved by controlling one or more synthesizers
in real time. Thus, the editor must incorporate process
control functions in addition to the various editing
operations. This real-time aspect differentiates interactive score editors from text editors.
This paper surveys problems related to interactive score
editing. The time factor is given particular consideration. A score editor for microcomputers, called INTERSCORE, is referred to for examples.
2. AN OVERVIEW OF INTERSCORE
INTERSCORE [Prusinkiewicz (1984)] is an interactive
score editor for microcomputers, loosely inspired by
GROOVE [Mathews & Moore (1970)1 It is written in C,
in a modular and structured way. It is therefore relatively easy to introduce modifications for the purpose of
testing various aspects of the man-machine interface as
well as for studying alternative system structures.
INTERSCORE is implemented on the Apple Ile microcomputer (*), with a five-octave alphaSyntauri (**) keyboard and Mountain Computer Music System (+) synthesizer boards. A joystick and two pedals (used to control the progress of time) complete the hardware
configuration.
The editor provides the composer with both audio and
visual feedback. An example of the screen display
when editing is shown in Fig. 1. The central part of the
screen is thought of as a window in which the selected
portion of the score is visualized using the piano-roll
notation [Buxton, Sniderman, Reeves, Patel & Baecker
(1979), Krasner (1980)]. A non-continuous line indicates two or more instruments playing in unison. Wide
lines near the top and the bottom of the screen show
the current position of the time cursor. The notes
corresponding to this position are being played by the
(*) Apple Ie is a trademark of Apple Computer Inc.
(**) alphaSyntauri is a trademark of Syntauri Corp.
(+) Music System is a trademark of Mountain Computer Corp.
275
ICMC '84 Proceedings
0
