Wavetable synthesis

A wavetable is a list of single-cycle waveforms lined up in order, often called frames. A basic oscillator plays one fixed shape. A wavetable oscillator adds a position control that picks which frame plays, and most wavetable synths blend neighboring frames as you move it, so the tone slides smoothly from one frame to the next.

That movement is what wavetables are for. Turn the position knob on a held C3 and the sound changes color while the pitch stays put, from hollow to buzzy or soft to glassy, depending on what is stored in the table. Put an LFO or an envelope on the position and each note changes shape by itself, which gives the evolving pads and talking basses wavetable synths are known for.

A table can hold the classic waveforms or anything else: frames drawn by hand, or single cycles cut from a recorded voice. After the oscillator, a wavetable synth usually works like a subtractive one, with a filter and envelopes shaping the result.

Wolfgang Palm developed wavetables you can sweep through at PPG in Germany in the late 1970s, and the PPG Wave synths of the early 1980s were built on them, with analog filters after the digital oscillators. In software, Xfer Records’ Serum and Vital, which has a free version, are two widely used wavetable synths.

In Gelato Synth, the Shape slider on the Osc A page morphs through a wavetable that runs from sine through triangle, saw and square to pulse, and the LFO page can target shape so the wave moves on its own. For how wavetable compares with FM and filter-based synths, see FM vs subtractive vs wavetable vs additive synthesis.