Store a series of single-cycle waveforms in a table, then scan through them while a note sounds. Here the table runs sine → triangle → saw → square, and the position knob crossfades between neighbours. Turn up scan and the position sweeps on its own — that moving timbre is the wavetable sound. We interpolate the partials' amplitudes and hand them to a band-limited oscillator, so scanning never aliases.
play with your keyboard (a s d f …) or click the keys