Propellerhead ReCycle! (1994)
Sample-based music was cutting edge in the early1990s, but before 1994, pitch and time were inextricably linked. If you wanted to increase the tempo of a sampled beat, the pitch would likewise increase – and vice-versa. ReCycle! changed all that, offering an intuitive means by which beats could be sliced, reordered, and played back at different tempos without affecting pitch, then offloaded into a hardware sampler. It was a watershed moment that pushed music into entirely new areas.