There are tons of products on the market that do this and have for years. Tasty Chips GR-1, GR-Mega and Mutable Clouds are some good examples but there are many, many other products on the market that do this. The essential premise of a modern granular sampler or delay is:
1. You have a large buffer that is constantly re-writing, sometimes tens of seconds long.
2. You have a “play head” that can mover around freely within that buffer and can be modulated.
3. From that playhead multiple Grains can play. There are multiple controls that affect how these grains play;
4. Grain Density, controls the polyphony of the engine. This can go from 1 voice up to hundreds.
5. Grain length, from a few ms up to seconds.
6. Grain Envelope. I.e. Rectangle, Trapezoid etc.
7. Grain Pan spread. Randomly or otherwise modulates the panning of individual grains.
8. Grain Pitch.
9 Jitter, randomizes the position relative to the playhead that a grain will play.
