Symptoms
- Some white or black keys sit higher or lower than their neighbours
- Key depth varies, so some notes need a deeper press to sound
- The keyboard line looks wavy when viewed from the end
- Uneven touch makes soft playing hard to control
Likely causes
Compressed front and balance punchings
Each key rests on felt punchings with paper shims. Over years of playing they compress at different rates, so keys drift out of level.
Humidity changes
Wood and felt swell and shrink with the seasons, which changes key height and can warp the key frame slightly.
Worn action felts
Worn hammer butts, backchecks and capstan felts change how far each key travels before the hammer fires.
Moving or a bumped key frame
Moving a piano or a knock to the keyboard can shift the key frame so it no longer sits flat on the keybed.
What you can safely check yourself
- 1Lay a straight ruler across the keys to see which ones are high or low.
- 2Look for a coin, pencil or other object under or between low or high keys.
- 3Check the room humidity and whether the unevenness changes with the season.
- 4Note whether it is a single key, a group, or the whole keyboard; a sudden change after a move suggests the key frame shifted.
What not to do
- Do not push down on high keys to flatten them or force low keys up.
- Do not add your own shims under keys; wrong thicknesses throw off depth and regulation.
- Do not loosen the screws holding the key frame.
Quick fixes vs. call a pro
You can usually handle it
- Spotting debris under a key
- Keeping humidity stable year-round
- Documenting which keys are uneven
Call a technician
- Leveling the keyboard with paper punchings
- Setting key depth evenly
- Re-seating a shifted key frame
- Full action regulation
What a technician will do
A technician levels the keys by adding or removing thin paper punchings under each key's balance rail, sets key depth with front-rail punchings, and adjusts the capstans so the action responds evenly. Leveling a keyboard usually takes 1-3 hours and is often combined with regulation.
A piano holds about 18–20 tonnes of string tension. If a fix means opening the action, turning tuning pins or working near the strings, leave it to a technician.
In Israel
Big seasonal swings between humid summers and dry, heated winters in places like Jerusalem and Safed make key height drift more noticeable over a year.