Time-Stretch Audio to Target BPM — No Pitch Change

Time-stretching changes the tempo (speed) of audio without changing its pitch. Unlike simple speed change that produces a "chipmunk" or "slowed" voice effect, time-stretching preserves the original tonality while only adjusting the tempo.

The algorithm reads BPM reliably on most music with a clear beat. If the detection is off, you can manually enter the correct BPM, use Tap Tempo, or use the half/double buttons to fix common octave errors (e.g. 60 detected instead of 120).

For changes within ±40% (ratio 0.6–1.4x), quality remains excellent. For larger changes, the algorithm chains multiple processing stages — quality may degrade slightly. A color indicator shows the expected quality for your ratio.

The Speed Changer is speed-first: you set a playback rate (e.g. 1.5x). This tool is BPM-first: you set a target BPM (e.g. 128) and the speed ratio is calculated automatically. It also includes genre presets, batch mode, and is designed specifically for DJ and remix workflows.

A jump that size is audible, and where it shows is the transients — a kick or a snare stretched by forty per cent loses its edge and starts to smear. The pitch stays where it was, so the track is still in key; what suffers is the attack. Ten or fifteen per cent is usually inaudible, which is why beat-matching works and why turning a ballad into a house track does not. Set A-B points over the busiest bar and audition that before committing to the whole file.

Yes: turn on “Straighten the tempo.” The tool finds every beat, shows how far the tempo wanders, and stretches the recording along a curve so the beats land on an even grid at the BPM you choose; the key doesn’t change. A regular BPM change stretches the whole file by one factor, so the drift stays. Tempo drift is most common in songs made by AI and in live recordings made without a metronome. Where the rhythm isn’t audible (an intro without drums, a breakdown), beats are placed from their neighbors.