Automatic Notation Of Computer-Generated Scores For Instruments, Voices And Electro-Acoustic Sounds

This article proposes a new software system for automatic representation and printing of computer-generated scores using traditional, proportional, and graphic notation. The software system includes a composition module (CMOD) and sound synthesis library (LASS)—both part of DISSCO— and an open source C++ vector-graphics library Belle, Bonne, Sage for music engraving. Various challenges to the process of music notation are noted, and a detailed description of the interface between DISSCO and Belle, Bonne, Sage is given. 1. BACKGROUND AND REQUIREMENTS Traditional Western notation reflects the changes Western music went through during the last seven or eight centuries. Among these changes is an increase in the complexity of its notation, culminating in the appearance in the second half of the twentieth century of new symbols and entirely new ways of representing music. The problem of music notation presents a wide range of challenges for music representation, for various reasons. It renders pitch versus time using symbols that address dynamics, articulations, clefs, harmonics, etc.; absolute proportionality of time and pitch is corrupted by the use of sharps and flats as well as by various symbols for individual durations; the notation of grace notes has more to do with longestablished conventions than with logic; etc. These challenges are compounded in some of the more recent schemes, like proportional notation, where time, frequency, and sometimes amplitude are seen in graph form; and graphic notation, where musical events are presented through a combination of drawings, text, and symbols, similar to the Augenmusik practiced by some Renaissance composers. Electroacoustic music has added a whole new class of challenges by employing either sounds whose parametric values are incongruent with those present in traditional music (for example, arbitrary frequencies or durations) or “objects” (textures) that are impossible to describe with the tools of the common practice period. In order to generate the score of a computer-assisted composition for instruments, voices, and/or electro-acoustic sounds, the alphanumeric output resulting from computations needs to be translated into some type of musical notation. Given the fact that even a relatively modest work includes thousands of sounds whose transcription when done by hand takes days, it is easy to see why one would want to avoid this tedious and error-prone activity. Furthermore, a tool for automatic transcription would enable a composer to see the results of his or her labors in a reasonable amount of time. Automatic transcription cannot be accomplished through the MIDI protocol (as available from some editing applications), because of its severe limitations both with respect to electro-acoustic textures and to contemporary instrumental or vocal extended techniques. A number of applications have addressed the issue, among them GrafPro, developed in 1989 at the University of Illinois Computer Music Project, which dealt successfully with the rhythmic complexities of traditional notation. (GrafPro is no longer in use, since the printing was done through the Score Music Publishing System, which has not kept up with recent developments in technology.) Pure Data (Pd), written by Miller Puckette [6], is capable of rendering graphic images of the electro-acoustic music objects it creates but does not handle traditional notation. Other applications such as Common Music Notation [7], the PWGL-Expressive Notation package [4], or FOMUS [5] have each solved some but not all of the necessary requirements: automatic processing of data; handling of both traditional, proportional, and graphic notation; dealing with instrumental/vocal parts as well as electro-acoustic sounds; and providing high quality, publishable documents. In this article we describe an automatic music notation interface between the computer-generated output for instruments, voices, and synthesized sounds (DISSCO) and an open source C++ vector-graphics library for music engraving (Belle, Bonne, Sage). [1]