Interpolation between frames

Interpolation between frames is how a wavetable oscillator blends its two neighboring frames when position lands between them, so timbre changes continuously instead of in audible steps.

Fractional positions weight the two adjacent frames, and most engines use a simple linear crossfade, which is cheap and transparent when neighboring frames are closely related. Higher-quality modes interpolate in the spectral domain, and some newer engines — Serum 2, for example — render intermediate frames on the fly so position behaves as a continuous control rather than a blend of two stored frames.