Wood expands and contracts with humidity, and repeated swings are the main long-term cause of soundboard cracks, tuning instability, and sticking keys in both grand and upright pianos.

How these systems work

An in-piano humidity control system combines a small humidifier, dehumidifier and a humidistat (a humidity-sensing thermostat equivalent) installed directly under the piano, keeping the immediate environment around the soundboard and pinblock within a stable range regardless of the room's swings.

Worth considering when

  • The piano is a higher-value or sentimental instrument.
  • It lives in a climate with pronounced seasonal humidity swings, or in a room without reliable climate control (e.g. near an exterior wall, a fireplace, or in a building without central humidity control).
  • The piano has already shown humidity-related symptoms like frequent tuning drift between seasons.

It is not a substitute for controlling humidity in the room generally (keeping the piano away from vents, radiators and direct sunlight still matters), but piano technicians commonly recommend it as a worthwhile addition for any piano that represents a meaningful investment.