Online Guitar Tuner — Mic Tuner

A clip-on tuner is the thing you never have when the guitar has been in the cold car. This Instrument Tuner uses the microphone on your phone or laptop instead. Pluck a string and it names the note, picks out which string you are on, and swings a needle to show how far sharp or flat you are, in cents. Each string button also plays its reference tone, so you can tune by ear with no microphone at all.

How to Use It on a Six-String Guitar

1. Leave the instrument on Guitar — standard and the reference on 440 Hz. The six targets read E2 82.41, A2 110.00, D3 146.83, G3 196.00, B3 246.94 and E4 329.63 Hz.
2. Press Start Tuner and allow the microphone. Pluck the low E and let it ring.
3. If the needle sits right of centre and the text says, for example, “18 cents sharp — tune down”, slacken the peg a little. When the reading falls within 5 cents, the needle, note and string button turn green.
4. Work across the strings. The tuner follows whichever string is closest, so you do not need to pick one first.

Load Sample steps through other set-ups: ukulele with its high G string, violin at A4 = 442 Hz as many orchestras tune, a four-string bass down to E1 at 41.20 Hz, and drop D.

How the Math Finds a Pitch

A plucked string is not a pure tone. The low E of a guitar often has more energy in its second and third harmonics than in the 82 Hz fundamental, which is why a simple spectrum peak tends to read it an octave high. The tuner uses the YIN method instead: it slides the waveform against a delayed copy of itself and looks for the delay at which the two line up, which is the period of the note however the energy is spread across its harmonics. That period is refined between samples, then converted to cents with 1200 × log₂(measured ÷ target). The median of the last five readings drives the needle, so a single bad frame does not make it jump.

Limits: Noise, Chords and A4

Play one string at a time. A strummed chord has several periods at once and the reading will wander. Background noise and speech below the level gate are ignored rather than shown as a note, and the detector covers 30 to 1,500 Hz, enough for a 5-string bass B0 at 30.87 Hz and a violin’s open E5 at 659.26 Hz. The browser’s echo cancellation and noise suppression are switched off for the microphone, since both are built for speech and flatten a sustained note.

The reference box accepts 415 to 466 Hz, which covers baroque pitch and A4 = 432. Anything else shows “Reference pitch A4 must be between 415 and 466 Hz” and the tuner keeps working at 440 until it is fixed. Audio is analysed in memory frame by frame and never recorded, uploaded or saved.