The short answer: twice a year for most homes

For the vast majority of domestic pianos in the UK, two tunings a year is the right rhythm. One in the autumn as the heating goes on, and one in the spring as it goes off. That pattern follows the two big seasonal shifts that pull a piano's pitch around, rather than fighting them.

It is worth understanding why twice, and not once or four times. A piano holds something in the region of 20 tonnes of tension across its strings. That tension is balanced against a wooden soundboard, a cast-iron frame, a pin block and a few hundred moving parts. Every one of those materials responds to changes in temperature and humidity. Left for a full year, a piano in a typical British living room will usually drop noticeably below concert pitch, and the tuning becomes not just a tuning but a pitch raise as well.

Twice a year is also the point at which most owners can stop thinking about it. Your technician arrives, the instrument comes back to A440, and it holds there comfortably until the next visit. If you take one thing from this article, take that.

Why pianos drift out of tune in the first place

A piano is in tune when the strings for each note sit at exactly the right tension. Several things push against that.

• Humidity. In damp weather the soundboard swells slightly, increasing the tension on the strings and pushing pitch up. In dry weather it shrinks, releasing tension and pulling pitch down. This is the single biggest influence on a domestic piano.
• Temperature. Less dramatic than humidity in most homes, but sudden swings — a piano beside a radiator, or a room that goes cold overnight — cause fast, uneven movement.
• Playing. Every hammer strike stretches the strings a fraction. The more the piano is played, the faster the tuning drifts, and the more unevenly it drifts across the keyboard.
• Settling. New string, new pin block, recently moved instrument — all of these take time to stabilise.

The result is that a piano never goes out of tune uniformly. Some notes drop a little, some a lot, and the unisons within a single note slip apart. That is the wobble or sourness you hear long before the whole instrument sounds obviously flat.

When twice a year is not enough

Plenty of pianos need more attention than the standard two visits. Book extra tunings if any of the following apply.

• A brand-new piano. In its first year or two, strings and structure are still settling. Four tunings a year for the first two years is common, dropping to two or three thereafter.
• A heavy practice schedule. A household where someone plays an hour or more a day, or where the piano is used for teaching, will usually want three or four tunings a year.
• A recently moved piano. Especially if it has come from a different climate, a different heating system or a long time in a van. Let it settle three to four weeks, then book a tuning — and expect it to need another one sooner than usual.
• Accompanying and performance work. Anyone playing with other instruments, singing or recording needs the piano at pitch on the day.
• A long-neglected instrument. If a piano has not been tuned for five or more years, it may need a pitch raise and then a second tuning a few weeks later to hold properly. It is not unusual for the first visit to be a stabilising exercise rather than a finished job.

The British climate, central heating and humidity

Our weather is genuinely hard on pianos. Outdoor humidity swings dramatically between summer and winter, and indoor humidity swings even more once the heating is running. A room that sits at a comfortable 50 per cent relative humidity in June can drop below 30 per cent in January without anyone noticing, and the piano notices long before you do.

Things that help in practice:

• Keep the piano away from radiators, log burners, underfloor heating zones, external walls and direct sunlight.
• Aim to keep the room between roughly 40 and 60 per cent relative humidity. An inexpensive hygrometer will tell you what you are actually dealing with.
• Use a room humidifier in dry winter months, or a dehumidifier in a damp room — but keep it stable rather than dramatic. Constant small corrections beat occasional big ones.
• For valuable instruments, ask your technician about a humidity control system fitted inside the piano itself.

Signs your piano is overdue, and what else might need doing

• Single notes that shimmer, wobble or sound like two notes at once — unisons have slipped.
• Octaves and chords that sound sour even though they were fine a few months ago.
• An overall dullness or sluggishness across the whole keyboard.
• Sticking or slow-returning keys, often a humidity problem rather than a tuning one.
• Buzzes, rattles, squeaky pedals or a pedal that no longer does what it should.

These last few are not tuning issues, but a tuning visit is the natural moment to have them looked at. A technician can also advise on regulation and voicing, which most well-used pianos benefit from every three to five years. Regulation restores the evenness of touch and repetition; voicing adjusts the tone. Neither is a luxury if the piano is played seriously.

Care between tunings, and getting the most from a visit

You do not need to do much, but the small habits matter. Play the piano — regular playing keeps everything moving freely and shows up problems early. Dust the case and the keys with a soft dry cloth, and never spray polish onto the keys or the action. Keep drinks, plants and vases off the top of the instrument, because water damage is expensive and entirely avoidable. Wash hands before playing. Cover the piano with a cloth if you are decorating, as plaster dust is abrasive.

Expect to pay somewhere in the region of £60 to £100 for a standard tuning outside London, with city prices higher, and more again if a pitch raise or repair work is needed. Book three to four weeks ahead, and book your autumn slot early — September and October are the busiest weeks of the year for tuners.

Finally, keep a simple record: the date, who tuned it, and anything you noticed. That small note is genuinely useful, because a piano's history tells your technician far more than a single visit ever can. Tune it twice a year, keep it out of draughts and away from the radiator, and it will reward you for decades.