Virtual analog synthesis
Digital synthesizers that compute oscillators, filters and envelopes so they behave like analogue circuits.
By the late 1980s digital instruments like the Yamaha DX7 had made analogue synths look obsolete, and used Minimoogs went for pocket change. A decade later everyone wanted the fat, filtered sound back — without the tuning drift and limited polyphony. Sweden's Clavia is usually credited with the first commercially successful VA synth, the Nord Lead of 1995: subtractive synthesis, built out of DSP code. Roland's JP-8000 (1996) gave the world the supersaw, and the Access Virus (1997) became the trance producer's instrument of choice.
The hard part is the detail. Naive digital oscillators alias and naive filters self-oscillate wrongly, which pushed the field towards techniques such as PolyBLEP and zero-delay feedback. Today the difference from the originals is often easier to argue about on forums than to hear.