A piano holds roughly 20 tons of string tension across its frame, and that tension is constantly shifting the pitch of every string, even when the piano just sits in a room. Changes in humidity and temperature cause the wooden soundboard to expand and contract, which changes the tension on the strings and pulls them away from pitch.
That’s why tuning isn’t a one-time fix — it’s regular maintenance, like changing the oil in a car. A piano that’s tuned consistently holds its pitch far better than one that’s left for years between visits, since consistent string tension is easier to maintain than tension that’s swung wildly out and back.
What affects tuning stability
- Seasonal humidity swings (especially heating season)
- Direct sunlight or proximity to heating vents
- How often and how hard the piano is played
- The age and condition of the tuning pins and pinblock
If your piano sounds noticeably off, particularly after a change of season, that’s normal, and a sign it’s time for a tuning.