RWND: Halftime and Reverse Varispeed Effect by Thenatan Audio

RWND runs two separate engines, HALF and REVD, each with its own trigger, rate, mix and sync toggle. HALF lowers playback to half speed for as long as you hold it. REVD ramps the playback rate from +1 through zero to -1, so the audio decelerates, stops and rewinds in the way a tape reel changes direction, rather than starting backwards instantly.

RATE sets how long the speed change takes, not how long the effect lasts. Short ramps create a hard drop or snap, while longer ramps create a slow wind-down. Each side can lock to host tempo with 24 note values or run free from 10 to 2000 milliseconds. Releasing a trigger fades back to the dry signal in about 4 milliseconds.

Each engine has an independent dry/wet mix, which lets you place a halftime version underneath the original track or blend a reverse swell behind a vocal without replacing the line. At zero mix a side is bit-transparent. Both triggers are ordinary automatable parameters, so you can play them live or draw them into an automation lane.

The interface shows both sides at once with a live display of the speed multiplier and direction. Hovering a control shows a short description, and the window resizes from 50% to 200%.