Fix BPM drift. Lock any song to a steady grid.
Some songs just won't sit still. They rush the chorus, drag through the breakdown, and wander a couple of BPM either side of where they started. BPM Lock takes the drift out. Every beat gets stretched onto one constant, integer BPM, pitch completely untouched.
The same eight bars, in and out
Beats land where the band played them. The grid slips further out every bar.
Every beat rewritten onto the grid. Same performance, same pitch, steady tempo.
This is the difference between marking the beats and moving them. DJ software and DAWs only mark, which is why the grid that fit bar 1 is visibly wrong by the second chorus. BPM Lock rewrites the audio, so the corrected file is on the grid everywhere it opens. Why beatgrids drift →
How it works
- Drop a track. WAV, MP3, FLAC, AIFF or M4A. Nothing is uploaded: detection, stretching and encoding all run inside this browser tab.
- See the drift. Every beat is detected and snapped to the drum transient. You get the real tempo range, suspect beats flagged in amber, and full control to drag, add or delete markers before anything renders.
- Render and download. Every beat is stretched onto the constant grid, pitch untouched, starting exactly on the one. Out comes a DAW-ready WAV, AIFF or 320 kbps MP3.
What a locked file is for
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Acapellas that stay in time
Lock the record first, then run the locked file through whatever stem splitter you use. The vocal that comes out is already sitting on a constant grid, so it drops straight over a loop or an instrumental at the same BPM and holds for the whole track. Split the original first and the acapella inherits every bit of the drift, which is why a stem pulled from an old funk or soul record slides out of time by the second chorus no matter how many warp markers you put on it.
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Remixes, edits and mashups
A constant integer BPM means loops, one-shots and quantized MIDI line up against the track without warping anything. Bar 1 starts on the one, so the file drops into a session at the project tempo and stays there.
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DJ sets and library prep
The beatgrid your DJ software writes for a locked file is correct for the entire song rather than the first sixteen bars, so long blends and loop rolls do not drift apart. The Rekordbox XML comes out alongside the audio.
More on fixing tempo
- Why beatgrids drift Why marking the beats cannot fix a moving target, and what rewriting the timing does instead.
- Fix the BPM in old songs and live recordings Funk, soul, disco, classic rock, hand-played house: the records that break auto-warp.
- Set a song to a metronome tempo Locking a whole track to one integer BPM, and why the tempo is not a control.
Frequently asked questions
- How do I fix BPM drift in a song?
- Drop the song into BPM Lock. It detects every beat, shows you how far the tempo drifts, and time-stretches each beat onto a constant BPM grid of your choice, without changing the pitch. You get back an audio file that plays at one steady tempo from the first bar to the last.
- Why does my beatgrid drift on old records?
- Because the song itself drifts. Music played without a click speeds up and slows down, so no single fixed grid can match it. DJ software and DAWs only mark where they think the beats are, leaving the audio untouched, so the marks slip further out the longer the track runs. BPM Lock fixes the cause instead: it stretches the audio so the beats genuinely land on a steady grid.
- Can I set a song to a metronome or click track tempo?
- Yes. That is exactly what BPM Lock does: it locks every beat of the song to a metronome-steady grid at an integer BPM. You can audition the original audio against a click track before rendering to confirm the grid is right.
- Does fixing the tempo change the pitch of the song?
- No. BPM Lock uses pitch-preserving time stretching. Only the timing changes, typically by less than a couple of percent per beat, which is inaudible.
- How is this different from warping in a DAW like Ableton?
- DAW auto-warp guesses a grid, struggles with human-played music, and the result only exists inside that one project. BPM Lock renders a new audio file that is permanently locked to a constant BPM, so it drops into any DAW or DJ software at bar 1 with no warp markers and nothing to re-analyse.
- Can I get an acapella that stays in time?
- BPM Lock does not split stems itself, but it fixes the thing that makes a split acapella unusable. Run the locked file through your stem splitter instead of the original: the whole track is already on a constant grid, so the vocal comes out in time from the first bar and sits over a loop or an instrumental at the same BPM without warping. Split the drifting original and the acapella drifts with it.
- What music does BPM drift correction work best on?
- Anything played by humans without a click: old funk, soul and disco records, live recordings, classic rock, hand-played house. Grid-quantized modern tracks pass through nearly untouched.
- Is my song uploaded to a server?
- No. Beat detection, time stretching and encoding all run inside your browser. The audio never leaves your machine, so unreleased promos and white labels stay private.