This paper presents an overview of a generic task model of music composition,developed as part of a research project investigating methods of improvinguser-interface designs for music software (in particular focusing on soundsynthesis tools). The task model has been produced by applying recentlydeveloped task analysis techniques to the complex and creative task of musiccomposition. The model itself describes the purely practical aspects ofmusic composition, avoiding any attempt to include the aesthetic motivationsand concerns of composers. We go on to illustrate the application of thetask model to software design by describing various parts of Modalyser, agraphical user-interface program designed by the author for creatingmusical sounds with IRCAM's Modalys physical modelling synthesissoftware. The task model is not yet complete at all levels and requiresfurther refinement, but is deemed to be sufficiently comprehensive to meritpresentation here. Although developed for assisting in software design, thetask model may be of wider interest to those concerned with the education ofmusic composition and research into music composition generally. This paperhas been developed from a short presentation given at the First Sonic ArtsNetwork Conference in January 1998.