This segment from Bitwig's Modular Concepts series walks through phase distortion synthesis inside the Polymer instrument, showing how the oscillator's wave shape algorithms shift a sine wave into a saw and other complex waveforms by distorting the phase of the signal rather than filtering it.
A key practical move here is routing an envelope directly to the wave shape parameter instead of a filter cutoff. This gives you per-note timbre morphing with a similar feel to a filter sweep, but the behavior is fundamentally different: at its resting position, phase distortion preserves a clean sine wave, whereas a low-pass filter pulled all the way down removes the fundamental entirely.
The host also points out that Polymer's sine and triangle oscillators include skew parameters that work on the same principle, misreading the waveform to push it toward a different shape. If you're already using those, you're working with the same sensibility as phase distortion, and combining them opens up a wider range of morphing possibilities.