Some ideas for random LFOs that go beyond sample and hold:
- Bounded random walk that randomly increases or decreases, but never jumps far from the previous value. This is basically an integrated and bounded (clipped) sample-and-hold, where a sampled value is added to the previous value at every step.
- Filtered noise LFO. The rate knob could affect the low-pass filter of the noise, so minimizing it gets you very slow changes and maximizing it just gets you white noise to modulate things, like you might on classic analog synths that include noise as modulation sources. This is basically a continuous sample-and-hold.
- Combining the two above ideas, a brownian motion LFO. Integrate the filtered noise and you get a modulation source that smoothly and randomly walks up and down.
