# BPM Changer

> To change a song's BPM without changing its pitch, time-stretch it. Load the file above: the tool detects the original BPM, you set a new BPM (slider or ±1/5/10 buttons, from 50% to 150% of the original), and Preview plays it at the new tempo with the pitch kept. Download WAV renders the change on your device using WSOLA time-stretching (which re-joins tiny slices of audio at matching points so the tempo changes but the pitch doesn't). The file is never uploaded. Small changes (±10%) sound most natural. Want the pitch to move too — the slowed or nightcore sound? Use the slowed + reverb maker.

URL: https://kenerateai.com/bpm-changer
Publisher: Kenerate AI (https://kenerateai.com)
Last updated: 28 September 2026

## Key facts
- Range: 50%–150% of the original tempo
- Pitch: Kept (time-stretch)
- Privacy: Processed locally
- Export: WAV, free
- Demo "Crate Digger" (Boom-bap, MiniMax Music 3.0): prompt: Classic boom-bap hip-hop beat, dusty kick and snare, chopped soul sample, deep bass, head-nod groove, 90 bpm
- Demo "Rio Afternoon" (Bossa nova, Ken Music 1.5): prompt: Bossa nova, nylon-string guitar, soft brushes, flute melody, warm and breezy, Rio beach afternoon, 124 bpm
- Demo "Hands Up" (EDM, MiniMax Music 3.0): prompt: Big-room EDM festival track, huge build-up, massive drop with punchy kick and lead synth, crowd energy, 128 bpm
- Demo "Last Set" (Jazz trio, Ken Music 1.5): prompt: Jazz piano trio, swinging piano solo, upright bass, brushed drums, late-night club, 132 bpm

## Steps
1. Choose a file — MP3, WAV, M4A or OGG, up to 60 MB.
2. Check the detected BPM — The slider starts at the original tempo.
3. Set the new BPM — Slider or ±1 / ±5 / ±10.
4. Preview — Pitch stays the same.
5. Download the WAV — Rendered on your device.

## In depth

### How time-stretching works
Simply playing audio faster raises its pitch. Time-stretching avoids that by cutting the audio into tiny overlapping slices and re-joining them closer together (faster) or further apart (slower). WSOLA picks each join point where the waveforms match best, which keeps the result smooth.

### Uses
Why people change BPM:
- Musicians — learn fast parts slowly.
- DJs — match tempos between tracks.
- Editors — fit music to a scene.
- Runners and dancers — match a cadence.

References:
[1] MDN — HTMLMediaElement.preservesPitch: https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/preservesPitch

## FAQ
Q: How do I change the BPM of a song?
A: Load it into the BPM changer above, set the new BPM, preview it and download the WAV. The tempo changes; the pitch stays the same.

Q: Can I speed up a song without changing the pitch?
A: Yes — that's what time-stretching does. The preview uses your browser's pitch-preserving playback, and the export uses WSOLA time-stretching.

Q: Is the BPM changer free?
A: Yes — free, no sign-up, and it runs on your device.

Q: Is my file uploaded?
A: No. Detection, preview and export all happen in your browser.

Q: How much can I change the tempo?
A: From 50% to 150% of the original. Changes within about ±10% sound the most natural.

Q: What's the difference between this and slowed + reverb?
A: The BPM changer keeps the pitch. Slowed + reverb (and nightcore) change speed and pitch together, like a turntable.

## Related pages
- BPM & key finder: https://kenerateai.com/bpm-key-finder
- Slowed + reverb maker: https://kenerateai.com/slowed-reverb-maker
- Click track generator: https://kenerateai.com/click-track-generator
- AI beat maker: https://kenerateai.com/ai-beat-maker

## Sources
- MDN — Web Audio API: https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API