20.5 Music as an open compositional domain

Music is a particularly revealing open domain because it is simultaneously formal, embodied, temporal, cultural, and affective. A modest musical sketch can contain pitches, durations, timbres, motifs, voices, chords, and sections. Its operations may include transposition, inversion, augmentation, orchestration, repetition, variation, and voice leading. Equations and limits can express metrical alignment, harmonic expectations, contrapuntal constraints, formal return, and instrument ranges. Models of the same declaration may live as scores, performances, MIDI events, symbolic analyses, or audio distributions.

This makes music a richer target than sequence continuation. Assimilation could improve a melody, accompaniment, orchestration, or performance within a declared musical grammar. Proto-accommodation could propose a new transformation, tuning relation, rhythmic grammar, timbral operation, or large-scale form; admitted accommodation would install it as a package change. Their interaction might reveal that an artistic intention is not expressible by the admitted operations. But an unfamiliar chord, high model loss, or surprising sound is not yet evidence for a new musical language. The residual must persist across examples and support a reusable operation.