Transpose by semitones without touching tempo, stretch tempo without touching pitch, or tie them together like a turntable. Everything is computed on this machine.
The file is decoded, analysed and rendered inside your browser, and never leaves this machine.
This free online pitch and tempo changer transposes the key of a song without altering its speed, and changes its speed without altering its key. Singers drop a track one or two semitones to reach the top notes, and players slow a solo to 70 % to learn it without hearing a chipmunk.
The whole engine runs in your browser: the file is decoded with Web Audio, analysed for key and tempo, and time-stretched with the formant-preserving Signalsmith Stretch engine compiled to WebAssembly. No queue — it runs in your browser.
Key, tempo and the ink waveform appear within seconds, measured locally.
Semitones, cents and tempo percentage each have their own control, with the resulting key and BPM printed live.
Drag an A–B loop to practise a passage, then download a WAV that lines up in your DAW.