Instrument Tuner

About this tool

The tuner uses autocorrelation to find the fundamental frequency of what it hears. Each reading takes a 4096-sample snapshot of the incoming signal and slides it against itself, looking for the time lag at which the waveform best matches its own copy — that lag is the period of the note, so its reciprocal is the pitch. This works far better than picking the loudest frequency from a spectrum, because a plucked string is rich in harmonics that are often louder than the fundamental itself. A parabolic fit around the correlation peak gives sub-sample accuracy, so the cents readout is stable rather than jumping in 5-cent steps.

All of that happens locally in your browser, sample by sample, and the audio is discarded immediately after it has been measured. Nothing is recorded or uploaded, and the microphone is released as soon as you stop.