Online Metronome

Practice timing with a precision online metronome built as a mechanical instrument: drag the brass weight to set 30–240 BPM, watch the pendulum swing on the audio clock, and copy a link with your setup. Every click is synthesized in the browser with the Web Audio API.

How to use it

1. Drag the brass weight or use the tempo controls. Tempo maps to the reciprocal of the weight’s distance from the pivot, as on a physical metronome; the slider and the −5, −1, +1 and +5 buttons set the same values in numbers, from 30 to 240 BPM. The default 120 BPM is one beat every 500 ms.
2. Choose a meter and a click sound. Free pulse, 2/4, 3/4, 4/4, 5/4, 6/8 or 7/8 for the bar, plus Woodblock, Beep, Tick, Rim or Cowbell for the click, with a volume slider and a mute button.
3. Add a subdivision if you need one. Off, Eighths, Triplets or 16ths, placed at 1/2, 1/3 or 1/4 of each beat at a lower level so the downbeat stays on top. For dedicated practice with subdivided grids, use the metronome with subdivisions.
4. Start the click with Space or the Start button. The pendulum, escapement wheel and beat tape all advance from the same scheduled beat events as the audio.
5. Tap the tempo with T or the Tap tempo button. Each tap previews a click; a gap of more than 3 seconds clears the sequence. To calculate the BPM of a song or live performance without an audible click, use the dedicated tap tempo tool.
6. Copy the link to share the setup. The URL carries bpm, sig and sub parameters (?bpm=120&sig=4&sub=2), and your last settings are remembered on this device.

The instrument: weight, pendulum and beat tape

Physical metronomes are reciprocal devices: sliding the weight toward the pivot shortens the period and raises the tempo, and the engraved scale here reads in real BPM. The pendulum angle comes from the same clock that schedules the clicks, so the swing extreme and the tick are one event at any tempo. The escapement advances one tooth per beat, and the beat tape records each measure as it plays.

Keyboard control is part of the instrument: ↑/↓ or ←/→ move 1 BPM, holding Shift makes each press 5 BPM, T taps tempo, Space starts and stops, and Escape leaves stage mode.

The lookahead scheduler

Calling setInterval() to trigger audio directly runs that callback on the main thread beside layout and script work, so beats arrive with tens of milliseconds of jitter and drift over time. The lookahead pattern avoids that: a timer checks every 25 ms and queues any beat that falls inside the next 250 ms on the audio context’s clock, which renders each click at its scheduled sample. A busy main thread cannot move a beat that is already queued, and when the page is hidden the window widens to 1.5 seconds so browser timer throttling cannot starve the click train.

Technical specifications

Specification	Implementation
Audio scheduler	Web Audio lookahead scheduler (25 ms timer check, 250 ms lookahead queue)
Background tab window	1.5 s lookahead window when hidden to prevent browser timer throttling
Tempo range	30–240 BPM
Time signatures (meters)	Free pulse, 2/4, 3/4, 4/4, 5/4, 6/8, 7/8
Subdivisions	Off, eighths (1/2), triplets (1/3), 16ths (1/4)
Tap tempo buffer	Rolling average of intervals; automatically resets after 3 s of inactivity
URL parameters	?bpm=30-240&sig=2-7&sub=1-4 for shareable configurations

Speed trainer and second voice

The speed trainer raises the tempo by a set number of BPM every set number of bars: step 1–50 BPM, every 1–16 bars, up to 240 BPM, defaulting to 5 BPM every 2 bars to 200 BPM. The readout flashes each new tempo.

Polyrhythm adds a second independent voice. Preset ratios of 3:2, 4:3, 5:4 and 5:3 lock it to the primary grid so the cycle closes exactly; Custom gives it its own tempo from 30 to 240 BPM, its own subdivision and its own level. Voice 2 can be muted on its own.

Tempo markings

The plate under the pendulum names the current BPM; the names describe character rather than speed, so the boundaries are approximate by tradition.

Marking	BPM on this tool	Character
Grave	30–39	Solemn and very slow
Largo	40–59	Broad and sustained
Larghetto	60–65	Calm, slightly faster than largo
Adagio	66–75	Slow and expressive
Andante	76–107	Walking pace
Moderato	108–119	Moderate
Allegro	120–155	Fast and bright
Vivace	156–175	Lively
Presto	176–199	Very fast
Prestissimo	200–240	As fast as the tool counts

Presets jump to Largo 50, Adagio 70, Andante 90, Moderato 110, Allegro 130 and Vivace 165 BPM.

Meters and accent schemes

• Free pulse. One unaccented click per beat for speed bursts and neutral practice; there is no bar line to wait for.
• 2/4 and 3/4. Accent on beat 1 only, for marches and waltzes; at 120 BPM a 3/4 bar lasts 1.5 seconds.
• 4/4. Primary accent on beat 1 and a secondary accent on beat 3, the backbone of rock, pop and jazz.
• 5/4 and 7/8. Odd meters for progressive rock and Balkan folk; 5/4 accents beat 4 and 7/8 accents beats 3 and 5. For more asymmetric time signatures and complex meters, use the odd meter metronome.
• 6/8. Compound duple: accents on beats 1 and 4 for the two-pulse triplet feel behind jigs and shuffles.

This metronome vs Google’s built-in metronome

Google’s search results provide a built-in metronome widget designed for a quick tempo pulse directly in the browser. While convenient for basic timing reference, it does not provide subdivisions (eighths, triplets, 16ths), odd meters (such as 5/4 or 7/8), a progressive speed trainer, polyrhythm capabilities, full-viewport stage mode, or shareable settings links. This instrument is built for dedicated practice, combining the visual mechanics of a physical pendulum with sample-accurate Web Audio scheduling, compound and asymmetrical meters, and deep practice modes.

Accuracy, limits and troubleshooting

• Background tabs keep time. When the document is hidden the scheduler queues 1.5 seconds ahead, so the click train survives timer throttling; only the moving visuals pause until you return.
• Click-to-ear latency is the output buffer. The scheduler fixes the spacing, not the buffer delay, which runs from a few milliseconds to a few tens of milliseconds depending on device and sample rate.
• Bluetooth adds transport latency. The spacing stays regular, but the whole grid can sit late against a recording or a DAW.
• Display refresh is not the audio clock. The screen repaints at 60 or 120 Hz, so pendulum motion can look a frame behind while the sound is exact.
• Tempo taps are your timing. A pause of more than 3 seconds clears the sequence, and readings outside 30–240 BPM show as the nearest limit.
• Windows audio enhancements and similar DSP sit in the output path and can add colour and delay.
• Volume is digital. For a louder grid, route the output to a mixer rather than pushing the browser above unity.

Related tools

• Metronome Subdivisions — A focused metronome that spells out eighth, triplet and sixteenth subdivisions at 1/2, 1/3 and 1/4 of the beat.
• Audio Latency Test — Measure the signed millisecond offset between scheduled clicks and your taps to see your system’s real delay.
• Ear Training — Practice hearing EQ bands against pink noise and harmonic tones once timing is under control.
• Tone Generator — Generate a steady sine, square, triangle or sawtooth to check output levels against the click.