Granular synthesis
Sound chopped into thousands of millisecond-long grains, then scattered back out in a new order, density and pitch.
Each grain is a short snippet, typically 1–100 ms, with a smooth window so its edges don't click. By controlling grain density, length, read position and pitch, one recording can become a frozen chord, a cloud of noise or a voice stretched to a minute without changing key. That last trick underpins a lot of time-stretching.
The idea belongs to Iannis Xenakis, who wrote about "sonic grains" around 1960 and cut tape by hand to prove it. Curtis Roads built the first computer implementations in the 1970s, and Barry Truax got it running in real time in 1986. Today it sits inside every ambient plugin, usually behind a knob labelled "Texture".