Symptoms
- A visible crack along the grain of the soundboard
- A buzz or rattle on certain notes, sometimes only in dry weather
- Weak, short sustain compared to how the piano used to sound
- A rib under the board that has separated from it
Likely causes
Drying and shrinking
The soundboard is thin spruce. When it dries out repeatedly, it shrinks across the grain until the wood splits.
Humidity cycles
Years of swelling in humid seasons and shrinking in dry ones compress and stress the wood fibers.
Age
Over decades the board loses some of its crown — the slight arch that supports string pressure — which makes cracks more likely and reduces tone.
What you can safely check yourself
- 1Listen for buzzing: play each note and note which ones rattle.
- 2Check whether the buzz is worse in dry periods, which points to the board or ribs.
- 3Look for loose objects on or inside the piano — they cause buzzes too.
- 4Keep humidity steady at 40–50% to prevent the crack from widening.
What not to do
- Don't ignore a crack that buzzes — loose ribs can get worse.
- Don't fill the crack with glue, filler or tape yourself.
- Don't put the piano near a heater or AC vent, which can widen cracks.
Quick fixes vs. call a pro
You can usually handle it
- Ruling out loose objects as the source of buzzing
- Monitoring humidity
- Noting which notes buzz and when
Call a technician
- Locating the exact source of the buzz
- Regluing loose ribs or bridges
- Shimming a crack with spruce
- Assessing crown and downbearing
What a technician will do
A technician first confirms whether the crack actually affects the sound — many don't. A buzzing crack or loose rib can often be reglued or shimmed with a strip of spruce; small repairs can be done on site in a visit, while a full soundboard repair or replacement is a major workshop rebuild worth doing only on a high-quality piano.
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
Cracks often appear after years in rooms dried by air conditioning or winter heating, then a buzz shows up in the dry hamsin days. Keeping humidity steady year-round is the best protection.