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Beatmatch trainer.
Two loops start together, yours at the wrong tempo and in the wrong place. Nothing on the screen will tell you by how much — fix it with the fader and the platter, then find out how many bars the mix would actually have survived.
Ready
Two loops start together. Yours is at the wrong tempo and in the wrong place, and nothing on this screen will tell you by how much.
Use the fader for the tempo and the platter for the position. When you think it is there, lock it in and find out how many bars it would have survived.
Your deck
Waiting
128.00
BPMPitch fader
+0.00%
One millimetre of a 100 mm fader at ±8% is 0.205 BPM — which is why nobody sets this by looking at it.
Platter
Drag the wheel, or hold the arrows. Held, it runs a little fast or slow; released, the beat stays where you pushed it, exactly as a platter does.
Space to deal a mix · arrows to nudge · up and down for the fader
Level
Both tempos on screen. Learn what the errors sound like before you have to find them.
Drill
Tempo and position both wrong, as they are on a real record.
Tempo to practise at
Monitoring
Split puts your deck in the left ear and the one already playing in the right, which is how you will actually do it. Use headphones for it.
What is already playing
Rolling offbeat bass, rim on the skip. The default to match against.
What you are bringing in
Straight and dry, with a tom rolling into the one.
The score
How long would it have held?.
Every other trainer marks you out of a hundred. A hundred what?
A beatmatch has two errors in it and they are not the same kind of thing. Where your beat is is a position, fixable with one push of the platter and then done. How fast the gap is growing is a rate, and no amount of pushing fixes it — it comes back, at exactly the same speed, forever.
A percentage has to average those two, and averaging them throws away the only distinction that matters. So this scores in bars: the gap starts at whatever your position error was and grows by whatever your tempo error is worth, and the score is the bar at which the total reaches 20 milliseconds — the point where two drums stop being one sound. A blend is 16 or 32 bars, so the number lands somewhere you already have an instinct for.
It is a closed form with nothing fitted to it. Solve |p₀ + rate × bars| = 20 for the earliest positive answer and that is the whole scoring rule, checkable on a calculator.
The technique
Being slightly out beats being dead on
A position error pointing away from your drift is not a mistake — it is the best place to be.
Here is what falls out of writing the score as a length, and it is not what anybody teaches. If your deck is running a hair fast, the gap is going to move one way and one way only. Landing dead on the beat gives that gap the full 20 milliseconds to cross, and it crosses them in 13.7 bars. Landing a hair out on the side it is leaving gives it the whole 40 — and the blend lasts 27.3 bars instead, almost exactly twice as long.
Which is the arithmetic behind something good DJs do without describing it: on a record you know is pulling ahead, you let it sit a touch behind rather than centring it, so it spends the blend walking through the middle instead of leaving from it. The table is the same idea at five tempo errors.
| Tempo out by | Slip per bar | Dead on the beat | 10 ms with the drift | 10 ms against it |
|---|---|---|---|---|
| 0.02 BPM | 0.29 ms | 68.3 bars | 34.1 bars | 102.4 bars |
| 0.05 BPM | 0.73 ms | 27.3 bars | 13.7 bars | 41.0 bars |
| 0.1 BPM | 1.46 ms | 13.7 bars | 6.8 bars | 20.5 bars |
| 0.25 BPM | 3.65 ms | 5.5 bars | 2.7 bars | 8.2 bars |
| 0.5 BPM | 7.30 ms | 2.7 bars | 1.4 bars | 4.1 bars |
Every row is the same expression solved twice. 20 ms is the conservative line for two transients fusing into one percept; 60 ms is where nobody is calling it a mix any more. The trainer reports both.
The fader
One millimetre is a wrecked mix.
The instrument is coarser than its display, which is the whole reason beatmatching is a skill.
A pitch fader is 100 mm of travel. At ±8% over 128 BPM that is 20.48 BPM spread across the whole throw, so one millimetre of thumb is 0.205 BPM — and 0.205 BPM out flams after 6.7 bars. On the ±6% range it is finer, 0.154 BPM, and still nowhere near enough to survive a phrase.
This is why the display having two decimal places is a little bit of a lie, and why beatmatching by ear is not one act but a loop: set it roughly, hear it drift, correct, hear it drift less, correct again. Nobody sets a fader and walks away. The trainer scores the end of that loop rather than the start of it, which is why the clock keeps running while you fiddle.
The drills
Tempo and position, one at a time
Two errors at once is why this takes people months. They separate.
A beginner pushing the platter cannot tell whether the gap came back because the tempo is wrong or because they pushed too hard, so every attempt teaches them two things at once and neither of them clearly. Every other physical skill is taught by isolating the parts; nothing in this category does it.
Position only starts the tempos already matched. One push and it is right, and it stays right — which is what a solved position error feels like, and worth knowing before you meet an unsolved one. Tempo only starts in phase and out of tempo, so the gap opens while you look for the fader, and you learn what a rate sounds like rather than a position. Full mix is both, as a record is.
The three levels change the equipment rather than the difficulty. Warm-up shows both tempos, like a controller. Club shows yours and not theirs, which is a CDJ against a record already playing. Peak time shows no numbers at all — a fader with a range printed on it, which is what made this hard in the first place.
The evidence
What was measured, and how.
A trainer that drifts is marking you for its own error, and you would have no way to tell.
Everything the tool plays is worked out from its own position in the count, never added to the beat before it, so there is nothing for an error to accumulate into. Rendered for 20 minutes at 128 BPM, the 2,560 kicks in it land within 0.5 of a sample of where the tempo puts them, which is a hundredth of a millisecond, and the last one is 0.125 of a sample out, no worse than the first.
The check that matters more is the one on the claim itself. Two loops half a BPM apart were rendered from the same start and every kick in both was located in the audio: they first pass 20 ms apart at bar 2.75, against 2.74 from the arithmetic. The score the tool gives you is the same expression, so it is being checked against a rendering of itself rather than being asserted.
For comparison, the ordinary way to build a metronome or a loop player is to ask the browser for a timer. A timer takes a whole number of milliseconds and a beat at 128 BPM is 468.75 of them, so a loop driven by one runs 0.75 ms fast every single beat — 5.76 seconds out after an hour. Practising against that would teach you to correct for the tool. This is arithmetic about how timers work, not a test of anybody's product.
The two loops summed peak at 0.774 against a ceiling of one, so nothing clips on the downbeat — which is worth measuring, because clipping on the loudest beat does not sound like clipping, it sounds like a slightly nastier drum.
Sync
Why learn this at all
The argument is not about honour. It is about what happens when the grid is wrong.
Sync works, and there is no medal for refusing it. What it removes is the correction loop, and the reason to own that loop is simple: a beat grid is a guess about where a record's beats are, and it is wrong often enough to matter. Anything with a live drummer, anything edited by hand, anything older than the software, anything whose first downbeat was placed a fraction late — the grid slides, and beatgrid drift is the polite name for the mix that follows.
When that happens, sync holds two records confidently in the wrong relationship and nothing on the screen goes red. The only thing that saves it is somebody who heard it. That is the skill this is for, and once you have it you can use whatever you like — including sync, faster and with more attention left over for the actual mix.
When you are done here, the metronome is the next thing to practise against — a click will never drift towards you — and the transition timer does the same arithmetic on your own two records instead of on a pair of loops.
Honestly
What this cannot teach you
What it is not, so nobody finds out the hard way.
It cannot teach you a platter. The weight of a record under your fingers, how far a nudge actually goes, the difference between a slipmat that grips and one that does not — none of that is here, and dragging a circle on a screen is not it. What is here is the ear: hearing that two things are apart, hearing which way, and hearing whether it is getting worse.
It also plays loops rather than records. Loops have no intro, no breakdown and no moment where the drums drop out and take your reference with them, which is the situation that separates people who can beatmatch from people who can beatmatch to a kick. For that, put a record on against the metronome's gap trainer, which takes the click away for eight bars and gives you nothing to follow.
Nothing you do here leaves your machine, nothing is uploaded, and there is no account. Your attempts are kept in this browser and nowhere else.
Frequently asked
Common questions
How do I practise beatmatching without decks?+
This is that practice. Two loops start together, yours at a tempo it did not choose and in a position it did not choose, and your job is to bring it onto the other one using a pitch fader for the speed and a platter for the position — which is exactly the two controls you have on a real deck and exactly the order you use them in. What it cannot give you is the feel of a platter under your hand, so treat it as the ear half of the skill. The ear half is the half that takes months.
Why does it not show me how far out I am?+
Because the moment a meter is on screen you stop listening and start centring a needle, and centring a needle is a different skill that does not transfer to a booth. Everything is measured the whole time — it is simply not shown until you commit. When you do, you get the tempo error, the beat error, the downbeat, and how long the mix would have lasted, all at once.
What does the score in bars mean?+
It is how long the mix would have held before the two records were far enough apart to be heard as two drums instead of one. Two tempos separate at a fixed rate, so the answer is arithmetic: your beat starts some milliseconds out and moves some more milliseconds every bar, and the score is the bar at which the total passes 20 ms. A 20 ms gap is the conservative line for two hits fusing into one — kicks are more forgiving and hats less. A 32-bar blend is the usual length, so anything over 32 is a mix you would have got away with.
Why not just give me a percentage out of a hundred?+
Because a percentage would have to average two errors that are completely different in kind. Being a long way out of position with a perfect tempo is one nudge away from a perfect mix. Being dead on the beat with a tenth of a BPM wrong is a mix that is already dying and cannot be saved without touching the fader again. A percentage would score those two the same and tell you nothing about which one you just did. A length in bars separates them, and it is a unit you already think in.
How accurate is the tool itself?+
Measured rather than claimed, because a trainer that drifts is scoring you partly on its own error. Every drum in it is worked out from its own position in the count rather than added to the one before it, so nothing accumulates: rendered for 20 minutes at 128 BPM, the 2,560 kicks in it land within 0.5 of a sample of where the tempo puts them, which is 0.01134 of a millisecond at the very worst, and the last one is no further out than the first. Anything you can hear moving is you.
Is using sync cheating?+
No, and that is not the interesting question. What sync removes is the correction loop — the small adjustment every few bars that keeps two records together — and the reason to be able to do that loop yourself is that grids are wrong often enough to matter: live drummers, older records, anything edited by hand, anything whose first downbeat was placed a fraction out. When the grid is wrong, sync confidently holds two records in the wrong relationship and the only thing that saves the mix is an ear that noticed. Learn it so you can hear it, then use whatever you like.
What is a flam?+
Two drums close enough together to be one sound but not close enough to fuse, so instead of a kick you hear a kick with something on the front of it. It is the sound of a mix coming apart, and it appears long before anything you would call a trainwreck. Once you can hear a flam you can beatmatch; until then you are watching a waveform.
Why can I not hear the difference at all yet?+
Start on the position drill with the tempos already matched, and use the percussion loop against a kick rather than two kick patterns — two of the same drum are much harder to separate than two different ones. Turn the split cue on with headphones so your deck is in one ear. And use "hear it locked" first: it is far easier to notice a sound going wrong when you know what right sounds like.
What tempo should I practise at?+
The one you play at. The errors are not the same size at every tempo — half a BPM out at 174 slips about half as fast as half a BPM out at 128, because the beats are shorter and there are more of them — so practice at 128 does not directly transfer to drum and bass. The tempo buttons cover house through to 174.
Does it keep my results?+
Yes. Your attempts, your settings and your best clean run are remembered in this browser, so the trend is there next time. A clean run means a full 32-bar blend, on the right downbeat, without hearing the answer first. Nothing is sent anywhere — clearing your browser data clears it.
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DJ terms on this page: Beatmatching · Pitch fader · Pitch bend · Split cue · Trainwreck · Beatgrid drift · Downbeat · Sync · Full glossary