Change the key of a song by up to an octave either way without changing its speed, or speed it up and slow it down without the chipmunk effect. The processing is Signalsmith Stretch, an open-source time-stretch library, running on your device; several files come back together as a ZIP.
How it works
- Drop a song, a backing track or a voice recording.
- Set the semitones (−12 to +12) and the speed (0.5× to 2×), and listen.
- Download the result as MP3 or WAV.
Questions
- Does my file get uploaded?
- No. The models and all processing run inside your browser on your own device. You can verify this yourself: open your browser’s DevTools, watch the Network tab, and process a file: there are no uploads. After the first visit most tools also work fully offline.
- Does it sound natural?
- Small changes, a semitone or two, or 10–20% of speed, are hard to tell from the original. Big ones are audible on voices, which start to sound processed past five or six semitones; instruments hold up better than voices.
- Can I change the pitch and the speed together?
- Yes. They are independent settings: transpose a backing track into your key and slow it down to practise, in one pass.