Free Online Piano Tuner

A chromatic tuner tells you the pitch of the note you are playing. On a piano that is useful for one thing above all: finding out whether the instrument is still at A440. Pianos drift flat as strings settle and as the seasons change the soundboard, and many household pianos sit ten, twenty, or fifty cents below pitch without anyone noticing until they are played alongside another instrument. Play A4 (the A above middle C), then a few notes across the keyboard, and the cents display gives you the answer in seconds.

What a chromatic tuner cannot do is tune a piano. Piano tuning is not a matter of setting each note to the equal-tempered frequency. Piano strings are stiff, so their overtones run slightly sharp of true harmonics, a property called inharmonicity, and a piano tuned so that every fundamental reads zero cents would sound dull and out of tune with itself. Tuners stretch the octaves, with the treble progressively sharp and the bass progressively flat, by tens of cents at the extremes, and set each note by listening to beats between overtones rather than by reading a fundamental. Most notes also have two or three strings that must be matched to each other as a unison. Doing this well needs a tuning hammer, mutes, training, and the judgement to avoid breaking strings that together hold roughly eighteen tonnes of tension. If your piano is out of tune, this page tells you how far; a technician fixes it.

To get a clean reading, play one key at a time at a moderate dynamic and let the attack pass before you read. The hammer strike is noisy, and the tuner may flicker for a moment before it locks on. In the low bass the fundamental is weak and the tuner may report a higher partial, so judge the bass from the tenor octave rather than the bottom notes. In the top octave the tone decays fast, so read quickly. A key that reads unsteady or shows two competing pitches usually has a unison out, meaning one of its strings has drifted from the others, and that is a common reason a piano sounds sour even when the overall pitch is fine.

If your piano reads more than about twenty cents flat overall, tell the technician before the appointment. Bringing an instrument that far back to A440 needs a pitch raise, a preliminary pass to bring the tension up before the fine tuning, and it may need a second visit to stabilise. If the piano is used with other instruments, or in a school, check it at the start of each term and after any move or large change in humidity.

The pitch history display shows how each note behaves over the first second or two after the strike, which is where unisons reveal themselves: a clean unison holds a steady line, a poor one wavers as the strings beat against each other. Use the A = control if your ensemble tunes to 442 or if you want to see how far the piano is from a different reference.