A method and apparatus for the creation and playback of music and/or sound; such that each time a composition is played back, a different sound sequence may be generated. In one embodiment, during composition creation, artist(s) may define how the composition may vary from playback to playback using visually interactive display(s). The artist's definition may be embedded into a composition dataset. During playback, a composition data set may be processed by a playback device and/or a playback program, so that each time the composition is played-back a unique version may be generated. Variability during playback may include: the variable selection of alternative sound segment(s); variable editing of sound segment(s) during playback processing; variable placement of sound segment(s) during playback processing; the spawning of group(s) of alternative sound segments from initiating sound segment(s); and the combining and/or mixing of alternative sound segments in one or more sound channels. MIDI-like variable compositions and the variable use of sound segments comprised of MIDI-like command sequences are also disclosed.