How to tune a piano at home: what you can check, touch up, and leave to a technician

What a tuning actually involves

A piano has about 220 strings on a cast-iron frame. A technician tunes one note in the middle of the keyboard to the reference pitch (usually A4 = 440 Hz, the international standard the Piano Technicians Guild describes), sets the temperament octave, then tunes every other note by octaves, and finally each note's two or three strings to each other (the unisons).

Pianos are tuned with stretched octaves: slightly flat in the bass and sharp in the treble, because stiff strings make their overtones run sharp. So a tuner that shows every key at exactly 0 cents of equal temperament is not the goal: see stretch tuning.

Check a piano and touch up a drifted note

1. Check first. Play keys across the whole keyboard into a piano tuner app and see which ones have drifted, and whether the piano as a whole has dropped below pitch. Do nothing else yet.
2. Decide. If the whole piano is well below pitch, or many keys have drifted, book a technician. Touch up yourself only a few notes that are slightly out.
3. Mute the other strings. Most notes have two or three strings. Mute all but one with rubber mutes or a felt strip so you hear a single string.
4. Find the right pin. Follow the string you are tuning to its tuning pin. Turning the wrong pin is the most common way strings break.
5. Move the lever a tiny amount. With a proper tuning lever on the pin, move it by the smallest amount you can, then play the note firmly and read it again. Go slightly past the target and back down to it, so the pin settles.
6. Tune the other strings to it. Remove one mute at a time and tune each remaining string of the note until the beating between them disappears (a clean unison).

Why a piano far below pitch needs a pitch raise

When a piano has gone a long time without tuning, its pitch can drop well below A-440. Raising the strings changes the load on the frame, and tightening one string changes the pitch of strings already tuned, so one careful pass cannot get there. Technicians use a pitch raise: a first, rough pass that brings all the strings to about the right tension, then a fine tuning. The Guild notes that extreme changes may need two separate pitch adjustments.

As a conservative rule, Pianowise suggests a technician when a check shows the piano 15 cents or more below pitch, and warns against doing it yourself beyond 50 cents. These two thresholds are Pianowise's own guidance, not a published standard.

Leave these to a technician

• Tuning pins that are loose or will not hold a note.
• Broken strings, cracked bridges or a cracked soundboard.
• Sticking keys, buzzing, uneven touch: regulation and voicing.
• Raising or lowering the whole piano's pitch.
• Any piano you are not sure about, and any older piano with fragile strings.

Safety

Use a real piano tuning lever, never pliers or an adjustable wrench, which damage the pins. Move the lever in tiny steps and stop if a note does not respond: a string under tension can break and whip. Wear eye protection when working on strings.

Questions

Sources

1. Piano Technicians Guild, Pitch Raising (A-440, tuning frequency, pitch raise) ptg.org
2. N. H. Fletcher and T. D. Rossing, The Physics of Musical Instruments, 2nd ed. (Springer, 1998), §2.18 and chapter 12
3. O. L. Railsback, "Scale temperament as applied to piano tuning", J. Acoust. Soc. Am. 9 (1938) 274