A timbre-dependent pitch helix, with instrument-dependent rotations per octave, in real Jukebox, MERT, and MusicGen

A 2026 study (arXiv:2607.29086) feeds isolated musical notes across a wide range of instrument timbres into real generative music foundation models (Jukebox and MERT, with consistent results reported for MusicGen), extracting layer-wise representations and fitting the combined linear-pitch-height-plus-circular-chroma (helical) geometry via PCA [do-music-foundation-models-embed-pitch-in-helical-structure-2026] The helix's clarity and rotations-per-octave depend systematically on instrument timbre -- e.g. Hammond organ yields a clean one-rotation-per-octave helix while electric clean guitar yields two rotations per octave -- with the effect traced to specific harmonics of the input signal, not merely to which model or layer is probed [do-music-foundation-models-embed-pitch-in-helical-structure-2026]