1. Damage to the Soundboard
The soundboard is the large piece of wood underneath a grand piano, and behind an upright. Cracks and warping of the soundboard alter the piano’s timbre, and can lead to strange buzzing and rattling sounds.
- Check if any reinforcement “ribs” have come unglued from the soundboard. If this has happened, the two will vibrate against each other, so listen carefully for even slight buzzing when keys are pressed.
- Check the bridge (the wooden piece holding up the strings). If the bridge is cracked, uneven, or unglued from the soundboard, buzzing will occur, and further damage will follow.
2. Pinblock Health
The pinblock is a wooden piece near the bridge that holds the tuning pins for each string in place. If the wood is damaged, the tuning pins can loosen, causing buzzing sounds and bad pitch.
- Listen for keys that sound two or more different notes at the same time. Piano keys are usually attached to two or three strings, and a bad pinblock can allow just one of them to go out of tune, causing two distinct pitches.
- Observe the quality of the wood on the pinblock, and make sure there is no cracking or splintering. Check for loose tuning pins, and beware of any rusting on them or on strings.
Tip: Unless the used piano is a high-quality instrument such as Steinway or Baldwin, it wouldn’t make financial sense to replace a damaged pinblock.
3. Worn Hammers
Each hammerhead is covered in felt, and worn-down felt sacrifices timbre. Look for deep grooves on the hammers caused by strings, and make sure no wood is exposed through the felt. Play each key, and listen for a harsh, clumsy tone, especially in the treble keys. Do not try to re-glue felt; felt is attached to the hammer using tons of pressure.
Learn about exterior warning signs that you should look out for.