Computer-assisted composition with algorithmic implementations of pitch-perceptual theory

We describe a computer-assisted procedure for composing harmonic progressions that takes into account the perceptual processes underlying roughness (sensory dissonance) and the pitch of complex tones. First, the user specifies the outer voices and specific model parameters, including preferred values of the perceived roughness of each sonority, the pitch commonality of successive sonorities, and the pitch commonality of each sonority with a reference sonority. The model then generates different possible chords and progressions within these constraints. The user is free to change the constraints to limit the number of possible chords and to choose from the generated chords according to personal criteria. The compositional process thus involves repeated interaction between composer and computer. We offer examples of progressions composed in this way from Dans la chair/In the Flesh, a recent piece for orchestra by the