Sethares roughness of the Lead as it sweeps over three octaves against the other layers; white line = its current pitch. Valleys are consonant intervals.

Each layer is a sum of partials, s(t) = sum a_k sin(2 pi f_k t), with amplitudes a_k ~ k^-p (Bell: inharmonic partials). The mix is their superposition; two close partials beat at |f1-f2|. Roughness follows the Plomp-Levelt curves in Sethares' parametrisation (1993). Slow motion stretches audio time so the waves are visible.