MIDI-Informed Singing Accompaniment Generation in a Compositional Song Pipeline

Song generation aims to produce full songs with vocals and accompaniment from lyrics and text descriptions, yet end-to-end models remain data- and compute-intensive and provide limited editability. We advocate a compositional alternative that decomposes the task into melody composition, singing voice synthesis, and singing accompaniment generation. Central to our approach is MIDI-informed singing accompaniment generation (MIDI-SAG), which conditions accompaniment on the symbolic vocal-melody MIDI to improve rhythmic and harmonic alignment between singing and instrumentation. Moreover, beyond conventional SAG settings that assume continuously sung vocals, compositional song generation features intermittent vocals; we address this by combining explicit rhythmic/harmonic controls with audio continuation to keep the backing track consistent across vocal and non-vocal regions. With lightweight newly trained components requiring only 2.5k hours of audio on a single RTX 3090, our pipeline approaches the perceptual quality of recent open-source end-to-end baselines in several metrics. We provide audio demos and will open-source our model at https://composerflow.github.io/web/.