What is the primary source selected for pitch modulation in the Mod Matrix?

The primary source selected for pitch modulation in the Mod Matrix is most commonly the LFO (Low-Frequency Oscillator). An LFO is an ideal candidate for pitch modulation because it produces a consistent cyclic waveform that can be used to create vibrato effects or other periodic changes in pitch. By adjusting the rate and depth of the LFO, you can effectively control how much the pitch varies and how frequently it oscillates, making it a powerful tool for sound design.

In contrast, while an envelope can modulate pitch, it typically controls modulation based on a specific trigger event (like a note being played), leading to a more dynamic but less continuous change in pitch compared to an LFO. Filters are primarily used to shape the tonal character of a sound rather than modulate its pitch, while a sampler is focused on playback of recorded audio samples and does not primarily function as a source for pitch modulation within the modulation matrix. Hence, the LFO stands out as the most suitable and commonly used source for this purpose.