How to tune a piano

Tuning your own piano makes most sense when it has drifted a little since its last professional tuning, it holds a tuning well, and you're prepared to go slowly. Start by measuring it: a piano health check tells you in a minute how far it is from pitch and whether the bass and treble have drifted apart.

• Within about 15 cents of pitch: a normal tuning, which this guide describes.
• More than about 15 cents flat on average: a pitch raise first, then a fine tuning. Raising a whole piano puts tens of extra kilograms on every string; old strings can break.
• Pins that turn too easily, jump, or won't hold: stop. Loose pins need a technician.
• A rare, valuable or antique piano: leave it to a professional.

A piano has 88 keys but about 220 strings. In the bass each note has one or two thick wound strings; from the tenor upward each note has three strings tuned to the same pitch, called a unison. Each string runs from a hitch pin at the bottom, over the bridge and up to a tuning pin driven tightly into a laminated wooden block, the pin block. Friction between pin and block is what holds the tuning.

Because piano strings are stiff, each one's overtones are a little higher than whole-number multiples of its fundamental. To make octaves sound clean, tuners stretch the tuning: the treble goes progressively sharp and the bass flat compared to theoretical equal temperament. How much depends on the piano, which is why a tuner that measures your piano beats a fixed table.

• Tune in a quiet room, with the piano at its normal temperature and humidity. Don't tune right after moving it, or the day the heating or air-conditioning changes.
• Open the piano. On an upright, lift the lid and remove the upper front panel (it usually lifts off two clips or turns on two knobs). On a grand, slide out the music desk.
• Look for broken strings, rust on the strings or pins, and keys that stick. Fix or note these before you start.
• Fit the felt strip through the middle section, from about F3 to F4, so that only the middle string of each three-string unison sounds.

Most of the craft is in the lever hand. A pin doesn't just turn: the top of it twists before the part inside the block moves, and if you leave it twisted it will spring back within days. Setting the pin means leaving it with no twist.

• Find the right pin: play the key, watch which hammer moves, follow that string up to its pin with the torch. Pluck or mute it to be sure.
• Hold the lever close to vertical on an upright (pointing up, around 12 to 1 o'clock), or pointing roughly toward the tail on a grand. Keep it in line with the pin so you rotate it instead of bending it.
• Make tiny movements. A few degrees of rotation changes the pitch a lot; start with nudges and listen.
• Pull the pitch slightly above the target, then ease it down to the target. Ending on a gentle downward move leaves the pin set and the string stable.
• Strike the key firmly a few times (test blows) after tuning it. If the pitch moves, the string wasn't settled; tune it again.

1. 1

   Tune A4

   With the felt strip in place, tune the single sounding string of A4 to its target: 440 Hz, plus the small stretch your tuner shows for this piano.

2. 2

   Tune the temperament octave

   Tune one string of every note from F3 to F4 against the tuner. If you tune by ear, this is where you set the temperament by counting the beats of fourths, fifths and thirds.

3. 3

   Tune the unisons in the middle

   Pull the felt strip out one note at a time and tune the two outer strings of each note to the middle string you already tuned, until the three sound as one with no slow wavering (beats).

4. 4

   Tune the treble, upward

   Work up from F4 to the top note. Mute the outer strings with a wedge, tune the middle string to the tuner's target, then tune the unison. Check each new note as an octave against the one below: it should sound clean, without beats.

5. 5

   Tune the bass, downward

   Work down from F3 to the lowest note, the same way. In the low bass the tuner will ask for notes slightly flat of equal temperament; trust the stretch and check octaves and double octaves by ear.

6. 6

   Check the whole piano

   Play octaves up and down the keyboard, then chords and scales. Retune any unison that wavers and any note that stands out. Give every note a few test blows.

When a piano has dropped well below pitch, tuning it straight up to the target doesn't hold: as you raise the later strings, the extra load bends the soundboard and pulls the earlier ones flat again. Technicians do a pitch raise instead, a quick first pass that deliberately tunes each note a little above its target (overpull) so the whole piano settles close to pitch, followed by a normal fine tuning.

The Tune In Time app has a pitch-raise mode that computes the overpull for each key from your health check. On an old piano, or one that is more than about 30 cents flat, ask a technician: strings that haven't moved in years are the ones that break.

• Turning the wrong pin. Always confirm the string before you turn, especially at the breaks between sections.
• Big movements. Turning by feel in large steps is how strings break.
• Not setting the pin. If the tuning is gone in a few days, the pins were left twisted.
• Tuning only one string per note. Unisons out of tune sound worse than a whole piano slightly flat.
• Using a guitar or chromatic tuner without stretch. The piano will sound out of tune in octaves even though every note shows green.
• Tuning in a noisy room, or with the fridge or air-conditioning humming close by.

Stop and call a professional if a pin turns with almost no resistance or won't hold its pitch, a string breaks, you see cracks in the pin block or soundboard, the piano needs a large pitch raise, or the problem is in the action (keys that stick, repeat badly or play unevenly). Tuning won't fix regulation or voicing, and a technician will often spot problems before they get expensive.