Tuner

Tuner listens through your phone's microphone and tells you how far off the note is. It comes with the usual instruments (chromatic, guitar, bass, violin and more) and you can add your own if yours is not in the list.

It works out the pitch from both autocorrelation and the frequency spectrum, then refines the reading using phase information, which keeps the needle steady rather than jittery. A graph shows how your pitch drifts over time, useful when you are holding a long note. Beyond equal temperament it supports just intonation, Werckmeister, Kirnberger and other historical tunings, plus non-12-tone scales like 17, 19, 31 and 53 divisions of the octave.

If you like fiddling with the details, the concert pitch, FFT window size and type, and overlap are all adjustable.