Music Representation Issues, Techniques, and Systems

Music offers a challenging array of representation problems. As an art form, is distinguished by the presence of many relationships that can be treated mathematically, including rhythm and harmony. There are also many nonmathematical elements such as tension, expectancy, and emotion. Music can contain symbolic or structural relationships existing within and between the dimensions of pitch, time, timbre, harmony, tempo, rhythm, phrasing, and articulation. A further source of complexity is that music can mean printed notation, performance (instrument control) information, or resulting sounds. Finally, evolves with every new composition. There can be no true representation just as there can be no closed definition of music. These elements combine to make representation a rich field of study. Computers allow (and require) a formal approach to the study of representation. Computer programs demand that every detail of a representation be precisely specified, and the resulting precision allows experimentation and testing of new representations. The knowledge we gain from these experiments is useful in theory and in understanding by computer. Computers also allow the representation of dynamic, responsive, or interactive compositions, a concept that was hard to imagine before computing. Better representations also lead to more powerful human-computer interfaces and tools. This is an overview of some of the issues and techniques that arise in studies of representation. No attempt has been made to be exhaustive, so the reader is referred to the references and the other articles in this issue of Computer Music Journal for more information. In particular, I will omit any discussion of audio representations and transforms used in signal processing (see De Poll, Piccialli, and Roads, 1991), although this is an important part of representation. Levels of Representation