The opposite of subtractive: build a tone by adding sine waves. Fourier
says any periodic sound is a sum of harmonics — so a sawtooth is just 1/h
amplitudes, a square only the odd ones. Each partial here is a real oscillator, which is
why the bell preset can use inharmonic ratios (0.56, 0.92, 1.19…)
that no single periodic waveform could produce. Move the sliders and watch the spectrum.
play with your keyboard (a s d f …) or click the keys