Metronome

A metronome is only useful if you trust it. This one runs from 20 to 300 BPM, offers 2/4, 3/4, 4/4, and 6/8 with an accented downbeat, and includes Tap Tempo for finding the tempo of a recording by ear. It clicks through the Web Audio API in your browser, with a visual beat indicator for silent or muted practice.

How to Use

1. Set the tempo. Drag the slider or use the + and - buttons to reach any integer BPM between 20 and 300. The default is 120.
2. Pick a time signature. Choose 2/4, 3/4, 4/4, or 6/8. The indicator row redraws with one dot per beat in the measure.
3. Press Play. The first beat of each measure is accented; the current beat is highlighted as a larger blue dot.
4. Match a recording with Tap Tempo. Tap the button in time with the music several times. The averaged BPM replaces the current setting.
5. Change tempo mid-session. Moving the slider or pressing + / - while playing restarts the beat at the new interval immediately.

Tempo Math: From BPM to Milliseconds

The tool converts tempo to a click interval with one formula: interval = round(60000 / BPM) milliseconds. The table below shows the values the engine actually produces.

BPM	Interval	Typical context
20	3000 ms	Slow breathing or meditation pacing
60	1000 ms	One beat per second; slow ballads
90	667 ms	Medium practice tempo, marches
120	500 ms	Common pop and rock default
180	333 ms	Fast fiddle tunes, punk
300	200 ms	Upper limit; subdivision drills

Because the interval is rounded to a whole millisecond, extreme tempos are not perfectly exact, but the rounding error stays under half a millisecond per beat.

Worked Example: Building a Passage Up to Speed

Suppose a student can play a difficult run cleanly at 76 BPM but not faster. At 76 BPM the click lands every round(60000 / 76) = 789 ms. She plays the passage five times without a mistake, then moves the slider to 80 BPM, where the interval drops to round(60000 / 80) = 750 ms — a difference of 39 ms per beat, small enough that the hands barely notice. She repeats the climb in 4 BPM steps. When a step produces two mistakes, she returns to the previous tempo rather than pushing through, which keeps the muscle memory clean.

How the Click and Accents Are Generated

Each beat creates a short sine oscillator into a gain node at 0.3, ramping exponentially to 0.001 over 100 ms so the click ends without a pop. Beat one of the measure is pitched at 1000 Hz; every other beat is 800 Hz. The beat counter advances modulo the beats per measure, so a 4/4 measure cycles 1-2-3-4 and a 6/8 measure cycles 1-2-3-4-5-6.

Tap Tempo stores each tap’s Date.now() timestamp, trims the list to the most recent 8 entries, computes the gaps between consecutive taps, averages them, and converts back to BPM with the same 60000 / average formula. That averaging is why a slightly uneven tap does not throw the result off.

Tempo Markings You Will See on Sheet Music

Printed music usually names a tempo in Italian rather than a number. The table below maps the common markings to the BPM ranges most editors use, so you can pick a starting click quickly.

Marking	Approximate BPM	Feel
Largo	40-60	Broad and slow
Adagio	66-76	Leisurely
Andante	76-108	Walking pace
Moderato	108-120	Moderate
Allegro	120-168	Fast and bright
Presto	168-200	Very fast
Prestissimo	200 and up	As fast as possible

These are conventions, not laws. A conductor may take an Allegro at 130 or 150 depending on the passage, so treat the marking as a starting point and adjust until the music breathes.

Practice Methods and Common Mistakes

• Slow-first repetition. Start below the target tempo where the passage is error-free, then climb in small increments.
• Subdivision counting. At slow tempos, say “one-and-two-and” aloud so each click accounts for two notes.
• Displacement drills. Deliberately place a scale note on the off-beat to test whether you are truly locked to the click or just following the accent.
• Long-tone holds. Use a single click per measure (a slow 2/4) to sustain a note and check for wavering pitch or tension.

Turning the metronome on only after a mistake is a common habit; the click then becomes a punishment rather than a reference. Set it before you play so your internal pulse and the click agree from the first note.

The two real limits are scheduling and tab behavior. Beats are queued with setInterval, so if the browser tab is throttled or the main thread is busy, a click can arrive late; the tool does not use a look-ahead scheduler. It also cannot accent each sub-beat differently within 6/8, so compound meter is counted as six even beats with one accent rather than the traditional strong-weak-weak-strong-weak-weak pattern. For those needs, a dedicated metronome app with per-beat accent control is a better fit.

Related Tools

• Tone Generator — Generate a reference pitch for tuning.
• Stopwatch Timer — Time your practice sessions.
• Pomodoro Timer — Structure practice into focused intervals.
• Countdown Timer — Set a fixed duration for a drill.