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Key and BPM changer.
Type the tempo you want, not a percentage.
Take a track to an exact BPM with the key held, move the key on its own, or do what a pitch fader does and move both together. It reads the tempo off the file first, so the target is a number you already had in your head — and it tells you which key you land in.
Drop tracks to retime
WAV, AIFF, FLAC, MP3 or M4A. Drop a whole folder’s worth — one set of settings is applied to all of them and they come back as a single archive. Nothing is uploaded; the page makes no network request.
What key lock actually costs
Holding the pitch means cutting the record up.
Measured rather than asserted, and stated with the range where it stops being free.
Playing a record faster raises its pitch — that is one physical fact and there is no way around it. So a tool that speeds a track up while holding the key has to do something else entirely: chop the file into short overlapping pieces and re-join them slightly closer together, choosing each join so that the waveform continues rather than jumps. Done well you cannot hear it. Done badly you get the flanging, underwater quality that gives key lock its reputation.
The measurement that matters is whether every kick still lands where the ratio says it should. On a synthetic four-to-the-floor where every kick position is known exactly, moving 128 to anywhere between 124 and 132 puts the median kick within 0.29 ms of perfect and 95% of them within 3.9 ms. That is well under what anybody can hear, and it covers the range a pitch fader reaches.
Push further and it does start to cost. Out at 3.8 ms median and 11.8 ms at the 95th percentile — that is 128 taken to 120 or to 140 — the joins are working much harder, and on a sparse, exposed intro you may start to hear them. The tool does not stop you, because a big shift is sometimes exactly what you want, but this is where the honest answer stops being "you cannot tell".
The alternative is always there and it is free: turn key lock off and the record simply plays faster, like it would on a deck. It goes up in pitch, it has no artefacts whatsoever, and for anything inside a few per cent that is what most DJs would choose if anybody told them it was an option.
It reads the tempo before you ask for one
Every other tool of this kind gives you a percentage slider, which requires you to already know the tempo, do the arithmetic, and accept whatever rounding falls out. This one measures the file, shows you what it found, and takes a target: you type 126 and it works out that 128 needs -1.56%. In a queue every file is measured on its own, so a folder that is not all one tempo still all ends up at the number you asked for.
Key lock and pitch shift are the same control, backwards
Holding the key while the tempo moves and moving the key while the tempo stays are not two features — they are one operation pointed in opposite directions, which is why almost nothing offers both. Here they are the same panel: set a target tempo, decide whether the key follows, and add a separate shift in semitones if you want the record in a different key entirely. The wheel positions are worked out for you, which matters because they are not where anyone expects.
The mode with no artefacts is the one nobody sells you
When the key is allowed to follow the tempo, nothing is cut and re-joined at all — the whole record is simply played at a different rate, exactly as a turntable does it. That is not a fallback, it is the highest-quality option available and it stays perfect at any amount. Key lock is the one that costs something, because holding the pitch means overlapping and re-joining the file. This tool tells you which one it used, every time.
The three things it does
Which mode, and what it costs
They are the same operation pointed different ways, so the trade is different in each.
| Mode | What moves | What it costs |
|---|---|---|
| Turntable | Tempo and key together, exactly like a pitch fader. | Nothing at all. The record is played at a different rate and no part of it is cut or re-joined. Perfect at any amount — this is the cleanest option on the page. |
| Key lock | Tempo only. The key stays exactly where it started. | The file is re-joined about thirty times a second. Inside ±3% the median kick moves 0.29 ms; past ±7% it climbs and can become audible on an exposed intro. |
| Key lock + shift | Tempo to your target, key to a different one. | Both operations at once — the record is played at a new rate and then retimed back. Same cost as key lock, plus a resample that is transparent to about 87 dB. |
| Key only | Key moves, tempo stays exactly where it was. | The same two operations, arranged so the length comes out unchanged. Useful for putting a track into a key that fits the rest of a set without touching the groove. |
A semitone up moves you seven positions round the wheel, not one, because the wheel is arranged in fifths. 8A shifted up a semitone is 3A. That single fact is why pitch shifting almost never lands where a DJ expects it to, and the tool works it out for you.
Frequently asked
Common questions
Can I change the BPM without changing the pitch?+
Yes, and that is the default here. Drop a track, type the tempo you want, and the key stays exactly where it started — the same thing MASTER TEMPO does on a CDJ. It works by re-joining the file at points where the waveform already repeats, which is why it holds up on a four-to-the-floor record: the joins land between kicks rather than through them.
Can I change the key without changing the tempo?+
Yes. Leave the target tempo where the file already is and set a shift in semitones — the track comes back the same length, in a different key. It is the same machinery as key lock, arranged so the length ends up unchanged instead of changed. Worth knowing before you use it: a semitone up moves you seven positions round the Camelot wheel, so 8A becomes 3A.
How much can I change the tempo before it sounds bad?+
Measured rather than guessed: inside about ±3% — roughly ±4 BPM at club tempo — the median kick lands 0.29 ms from where it should and 95% land within 3.9 ms, which nobody can hear. Out at ±7% or more that rises to around 3.8 ms and it can start to show on a sparse intro. If you need a big change and it matters, turn key lock off — playing the record faster has no artefacts at any amount, it just goes up in pitch.
Which is better, key lock or letting the pitch move?+
Letting the pitch move is better, technically, and it is not close — nothing is cut and re-joined, so there is nothing to go wrong. The reason to use key lock is musical rather than technical: if you have built a set around a key, a record that drifts a semitone as you ride the fader stops fitting it. So the honest rule is to let the pitch move unless the key is doing work, and this tool makes both one click apart.
Does this work on a whole folder?+
Yes, and it does the thing that makes a batch worth having: every file is measured on its own before the ratio is worked out. Drop thirty tracks at a spread of tempos, ask for 128, and all thirty come back at 128 rather than all thirty being shifted by the same percentage. Each file gets its own report and the set comes back as one archive, named with the tempo so a stick stays readable.
What formats can it write?+
WAV, AIFF and FLAC if you want to keep every sample, and MP3 if the file is going somewhere that needs to be small. The lossless three are the right answer for anything you are going to play — a retimed track is a new file, and there is no reason to make it a lossy one when the original was not.
Does my track get uploaded?+
No. The file is decoded, retimed and written back out entirely inside this tab. There is no upload endpoint behind the page — open the network panel and watch it stay empty — which also means an unreleased promo is safe to drop on it.
Why does the tempo it detects not match Rekordbox?+
Usually because one of you is reading it at half or double speed, which is a real ambiguity rather than a mistake: a drum and bass record at 174 has a perfectly good pulse at 87. If the detected number is exactly half or double what you expect, type the target you actually want and the ratio still comes out right. The tempo the tool applies is the ratio between what it read and what you asked for, so a consistent halving cancels out.
Will the file still be beatgridded when I import it?+
It will need re-analysing, like any new file, and it will grid cleanly because the tempo is genuinely constant — the realised length is within 0.002% of the ratio you asked for on real records, which is far tighter than a beatgrid needs. The whole file can arrive a few milliseconds earlier or later than a perfect ratio would put it, which moves nothing musically and is re-cued on import anyway.
Can I use this to make an edit fit another track?+
That is the main reason to use it. If two records you want to play together are four BPM apart and you would rather not ride the fader through the whole blend, bring one to the other and the transition is a straight beatmatch. If they are also a semitone apart, the shift control closes that too — and the chemistry score on the track pages will tell you whether it was the tempo or the key that was in the way.
How big a file can it handle?+
Up to 800 MB, which is about 75 minutes of 24-bit stereo audio, so a whole recorded set works. Retiming itself is fast — several hundred times faster than playing the file — so the wait is mostly decoding and writing rather than the change you asked for.
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Key & BPM finder · Pitch and tempo calculator · Half-time and double-time · Camelot wheel · Audio converter · Score my transition · Key lock · Pitch shifter · Pitch fader · All tools
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DJ terms on this page: Key lock · Pitch shifter · Pitch fader · Camelot key · BPM · Harmonic mixing · Beatmatching · Musical key · Full glossary