Metronome

Clicks scheduled on the audio hardware clock, so the beat holds steady even when your browser doesn't. In tune is half the job — the other half lives here.

Using it with the tuner

Tune first, click second — a session that starts with the tuner and runs a passage at 80% speed against this click fixes more in ten minutes than an hour of noodling. Finding a song's tempo? Tap along with the button (four taps minimum; the count uses the median so one clumsy tap doesn't skew it).