Click a beat to change how it is played: accent → normal → quiet → silent. Silence is the useful one — muting beat 3 forces you to keep the bar yourself across the hole.
| Note value | Length | Rate |
|---|
The row in colour is the beat you are counting. These are the numbers you type into a delay pedal or a plug-in to make it land in time — a quarter-note delay is 60000 ÷ BPM milliseconds, and everything else follows from it.
The obvious way to build a metronome is a timer that goes off every 60000 ÷ BPM milliseconds. It does not work, and it fails in a way that is easy to miss: a browser timer promises at least that long, never exactly that long. Anything else the page or the machine is doing — a repaint, a garbage collection, another tab — pushes the callback late, and the click goes with it. Music needs the opposite guarantee.
Every click is handed to the audio hardware in advance, stamped with the exact moment it should sound, measured on the audio clock rather than the page's. A slow loop wakes about forty times a second and asks one question: is there a beat due in the next tenth of a second? If so it is scheduled and forgotten about. The loop can be late — it frequently is — without any of that lateness reaching your ears, because the beat was already in the queue before the loop overslept.
The This run panel measures both numbers while you play, and they are worth watching. The scheduler's own wake-ups wander by several milliseconds. The beat times it produces do not wander at all, because each one is computed from the last as an exact addition of 60 ÷ BPM seconds — the error cannot accumulate, since nothing is ever measured to produce it.
That distinction is the whole tool. A metronome that drifts by two milliseconds a beat is out by a third of a beat after two minutes at 100 BPM, which is the difference between practising with a reference and practising with an opinion.
Because a subdivision is not a faster tempo — it is a division of the beat you are already counting, and the difference matters when you read music. Eighth notes at 90 BPM and quarter notes at 180 BPM produce the same stream of clicks, but only one of them is the tempo written on the page. The clicks between beats are quieter here for the same reason: they are decoration on the pulse, not the pulse.
Moving the second half of each beat later. At 50% the two halves are equal and the feel is straight; at 66.7% the beat is split two-thirds/one-third, which is the same ratio as playing the first and third notes of a triplet and is what most people mean by swing. Past that it becomes a hard shuffle, and by 75% it is close to a dotted rhythm. The slider needs a two-part subdivision to be audible, because there is nothing to displace otherwise.
Because playing along with a click is a much easier skill than keeping time, and it is easy to spend years doing the first while believing you are doing the second. Two bars on, two bars off removes the crutch periodically and tells you the truth when it returns. Muting individual beats does the same thing at a smaller scale — a bar with only beat 1 clicking is a good deal harder to hold than it sounds.
Because seven beats in a bar is not a feel, and 3+2+2 is. Written as seven undifferentiated clicks a 7/8 is something to be counted; grouped, it becomes two long-short-short patterns your hands can learn. The grouping box sets the accents accordingly — type 2+2+3 and the same seven beats become a completely different piece of music.
Not really, and that is not a flaw in this page. Allegro is a character before it is a speed, the ranges overlap, and they have shifted over three centuries — Beethoven's markings are famously argued about. The word shown here is the conventional modern range and is offered as orientation, not as a definition.
That your device's audio clock runs at the rate it claims. Beat placement is exact against that clock, but the sound still travels through the operating system's output buffer, Bluetooth headphones, or a speaker in another room — each of which adds its own latency. That latency is constant, so it delays everything equally and does not affect timing between beats; it does mean that recording against this click and expecting sample-accurate alignment is a mistake. Browsers also throttle background tabs, so leave this one visible while it runs.
This page has changed in 2 archived releases, but each of those was a site-wide pass, so none is attributable to this tool on its own and none is listed here. That is not a claim that the tool never changed — a release that reworked many pages at once may well have altered this one too. The changelog has them.