Many owners assume an unplayed piano stays in tune. The opposite is true: the number-one cause of tuning drift is the moisture in the air.
Pianos go out of tune mainly because of humidity, not playing: the soundboard swells and shrinks with moisture, directly changing string tension and pitch. Add the natural relaxation of some 20 tonnes of string tension, and even an untouched piano drifts. In Hong Kong, tune at least once or twice a year.
A piano carries around 230 strings, each tensioned to nearly 90 kilograms โ together, the cast-iron plate bears roughly 18 to 20 tonnes of pull. Being "in tune" means every string's tension sits at exactly the right value, so that A vibrates 440 times per second (the A440 international pitch standard).
The catch: steel wire under constant tension relaxes naturally over time, stretching and softening as it ages. So going out of tune is never a question of "if", only "how fast" โ a piano nobody touches for a year will still have sunk in pitch.
Worth knowing: "out of tune" actually covers two different things. One is the whole piano slowly sinking below A440; the other is the strings within a single note drifting apart, producing a muddy, beating sound. The first comes mainly from tension relaxation and humidity; the second usually involves tuning pin stability โ a technician addresses both in one visit.
Bigger than natural relaxation is humidity. A piano's soundboard is not flat โ it is built with a slight arch called the crown, and the strings press down on it through the bridge. When humidity rises, the wood absorbs moisture and the crown swells upward, pushing the bridge harder against the strings โ tension rises and the whole piano drifts sharp. When humidity falls, the crown flattens, tension eases and pitch sinks.
Hong Kong puts this cycle on fast-forward: weeks above 90% humidity in the spring damp season, dry northerly winters below 40%, and the daily switch between air-conditioned and non-air-conditioned rooms. Your piano is breathing with the weather every single day โ the root reason pianos here drift faster than almost anywhere. A common example: a piano room air-conditioned by day (dry) and closed up at night (humid) can swing twenty to thirty percentage points in a single day โ the soundboard swells and shrinks daily, and no tuning can sit still through that. Stability, as technicians like to say, matters more than dryness. See our Hong Kong humidity guide for the full picture.
Completely normal, and unavoidable. New strings behave like new guitar strings: they need time to stretch in. For the first year or two the strings keep elongating and pitch sinks noticeably faster than on an older instrument, which is why many makers recommend two to four tunings in the first year before settling into a normal rhythm. Tuners also deliberately "set" each string โ easing it slightly sharp and settling it onto the exact pitch โ so the tuning holds longer. If your new piano drifts noticeably in its first year, it is not a quality problem โ quite the opposite: tuning it on the recommended schedule lets the strings finish stretching at the correct tension, which serves the instrumentโs long-term stability.
It contributes, but it is secondary. Every hammer blow nudges the strings microscopically, and years of playing do take a toll; loud, sustained playing โ concert preparation, exam practice โ has a visible effect. For a typical home piano, though, playing matters far less than humidity. "If nobody plays it, we can skip the tuning" is the most common misconception in the trade: the unplayed piano drifts just the same โ there is simply nobody there to hear it.
Four things keep pitch stable: hold indoor humidity around 42โ45%, with a dehumidifier in the damp season; place the piano away from AC airflow and windows (see the tuning frequency guide); book a professional tuning at least once or twice a year, more often for a new piano; and never let years slip by โ once pitch has sunk too far, the piano needs a pitch raise to pull the overall tension back up before a fine tuning can hold, sometimes over two visits. The Pro Piano's Steinway and Yamaha certified technicians check the action (piano action) and interior at every tuning, so each visit does more than just the pitch.
For a typical home piano, at least once or twice a year. New pianos need more โ often two to four tunings in the first year while the strings stretch in. A piano that sits unplayed still needs its regular tuning.
No. Tuning drift is driven mainly by humidity moving the soundboard and by the natural relaxation of some 20 tonnes of string tension โ neither has anything to do with playing. A year untouched, and the pitch will have sunk regardless.
Three common reasons: large temperature and humidity swings (AC blowing on the piano, a spot near a window), a new piano whose strings are still stretching, or too long a gap since the last tuning so the pitch had sunk too far to stabilise in one pass. Fixing placement and humidity makes a visible difference.
Not always. When pitch has dropped substantially, the technician first performs a pitch raise to pull the overall tension back up, lets the structure re-balance, then fine-tunes โ sometimes across two visits. Regular tuning is genuinely the cheaper path.
Not advisable. A piano has 230 strings under nearly 20 tonnes of combined tension, and good tuning is as much about setting the pin and string so they hold as about hitting the frequency. An inexperienced hand on the wrong pin risks broken strings or pinblock damage.
Piano not tuned in years โ or drifting soon after every tuning? Have a certified technician check the pitch and the interior, and find the real cause.
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