Higher-level Composition Control in Music Sketcher: Modifiers and Smart Harmony Steven Abrarns, Daniel V. Oppenheim, Don Pazel, James Wright Sabrams, music, pazel, jwrigoht @watson.ibm.com Computer Music Center T. J. Watson Research Center, IBM P.O. Box 218, Yorktown Heigohts, NY 10598 www. research. ibm.com/music Abstract There is a fundamental tension between working with high-level abstractions which often provide intuitive conceptual manipulations but hide details, and working with low-level data which, while quite powerful, can also be quite tedious. To help balance this tension, we have been developing technologies and higher-level abstractions designed to enhance the composer's ability to create music, focusing on the compositional concepts of shape, structure, and tension-release. This paper discusses our ongoing efforts in this area, as demonstrated in the Music Sketcher program, with particular focus on the Smart Harmony and Modifier technologies. 1. Introduction The typical user interface in many commercial music applications models machinery in a recording studio, such as a multi-track recorder and mixer. This model has little to do with the process of creating music that has been evolving for over a millennium by Western composers. Computer languages for composing music that are more commonly developed in academic environments share a similar problem. In these languages thle conceptual model is often a combination of some structural aspects of music as modeled by a musical score, with a focus on tools and processes that are often borrowed from computer science. Here the connection to traditional compositional process is also tenuous. At IBM Research's Computer Music Center (http://www.research. ibrn.comlmusic) we are engaged in a series of projects that revolve around music, art and creativity, with a goal of helping people to amplify their natural musical creativity. In particular we are beginning. to investigate some of the concepts used by composers in their creative process, starting with structure, shape, and tension-release. We feel that by focusing on concepts, rather than on machinery that happens to be available, we will be able to develop user interfaces, tools, and technologies, that are more meaningful to composers. This paper will focus on three novel mechanisms that we developed for dealing with these initial concepts: blocks, modifiers, and Smart Harmony. "Blocks" is our initial attempt at a technique for manipulating a composition's structural aspects. "Modifiers" allow reshaping aspects of the music at different structural levels, ranging from subtle expressive nuances to significant (and even radical) reworking of compositional materials [Oppenheim 92]. "Smart Harmony" models aspects of tonality - a mechanism used in Western music to create sensations of tension and release - and supports the creation of harmonic frameworks in a composition. These are all implemented in our Music Sketcher application, available for download at http://www.research. ibm.comn/music. Music Sketcher is a vehicle we are developingo for experimenting, generating ideas, and exploring the power of our new music technologies. It draws on our experience from D>MIX [Oppenheim 96] and builds upon our previous work with the CyberB and program [Wright et al 97]. Music Sketcher is unique in that it combines a model of tonal music with a system of high-level modifiers that supports a variety of sophisticated manipulations, all working together to maintain a desired musical context. Music is represented using a three-level content hierarchy (see Figure 2): a single ScoreSheet contains a set of ScoreParts, each containing one or more ScoreBlocks. The ScoreSheet represents the entire composition in a fairly conventional manner: time proceeds from left to right, and concurrent Parts are stacked vertically. A ScoreBlock (or Block) contains an ordered set of notes and other events, often corresponding to a musical phrase, motif or "rift" (a Ri~ff Block) or even a chord sequence (a Harmony Block). A Block could also contain entire sections or nested compositions: the underlying representation supports hierarchies of arbitrary depth (Music Sketcher does not currently use this capability). A parallel modifier hierarchy mirrors the multi-level content hierarchy and provides an intuitive mechanism for creating musical transformations. ICMtC Proceedings 1Y999 3
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