This plays a looping melody while you adjust the strength of multiples of the fundamental (harmonics) in real time. Pitch (notes) changes with the melody, but the harmonic mix controls timbre (quality).
While the loop plays, try moving higher harmonics up/down. The melody stays the same, but the instrument “character” changes.
Tip: browsers require a user click to start audio. If you hear nothing, click Start loop again.
Bars show the harmonic amplitudes you set (not an FFT). Harmonic 1× is the fundamental; 2×, 3×, ... are multiples.