Excerpted from The Piano Book, Fourth Edition, by Larry Fine
Find the serial number of the piano so you can look up its year of manufacture in the Pierce Piano Atlas. Usually four to eight digits, the serial number is most often located near the tuning pins, either printed directly on the plate or engraved in the wooden pinblock and showing through a cut-away portion of the plate. Or the number may be printed somewhere else on the plate or soundboard, printed or engraved on the top or back of a vertical piano back, or printed or engraved on the front edge of a grand piano key frame (Figure 1). (Sometimes a three- or four-digit number used in the manufacturing process also appears on various case parts; don’t confuse this with the serial number.) When no serial number can be found or if the year of manufacture isn’t listed in Pierce, sometimes a technician can estimate.
This video provides more details regarding serials numbers:
Here is a checklist you can copy and take with you when checking out a used piano. The list is a brief summary of the section “Checking Out the Piano.” I assume you have read the section and know how to remove the outer case parts of a piano to look inside. If you decide to proceed further with a piano after examining it with this list, you will need to hire the services of a professional piano technician to check some things you could not, such as the tightness (torque) of the tuning pins, and to render an experienced judgment about the piano as a whole.
Looks, styling and finish
Can you live with it?
Does it need refinishing?
Has it been restyled in an unusual way?
Does it have any missing or broken cabinet parts or hardware (music desk, hinges, etc.)?
Check for loose veneer and other signs of water damage.
Does a matching bench in good condition come with the piano?
Pinblock and tuning
Is the piano up to standard pitch? Is it in reasonable tune?
Badly out-of-tune unisons may be a sign of loose tuning pins, especially if the piano has been tuned recently or if the mistuning of the unisons is gross. The tuning pins should be checked by a technician.
Are tuning pins uniform in appearance, or are there some obvious replacements? The latter could indicate the pinblock is going bad.
Look for at least ⅛” clearance between tuning pins coils and the pinblock or plate.
Look for ugly, dark brown, gummy stains which indicate the pinblock has been doped with chemicals to temporarily tighten tuning pins.
On a grand, if you are able to remove the fallboard, look at the underside of the pinblock for signs of cracking and delaminating.
How rusty? Light rust or tarnish is okay, but excessive rust, especially on coils or at bearing points, is a problem, and could lead to breakage.
Are any strings missing?
Too many new-looking strings among the older ones indicates a breakage problem; too many splices, as well.
Do bass notes sound clear and resonant, or short and tubby?
Primary problem area is the bass bridge.
Some hairline cracks around bridge pins are customary.
Excessive cracks that cause dislocation of bridge pins, especially on bass bridge, are a big problem and indicate the need for a new bridge or bridge cap.
A piano with a loose bass bridge will have much weaker tone on one end of the bass section than the other.
Also check the treble bridge for serious cracking.
If piano is very old, check wooden upper bearing point for cracks.
Look for cracks in the plate, both in the struts and in the tuning pin area. Repairing a cracked plate is costly and usually not guaranteed. Cracked plates are very rare.
Look for separations or delaminations in the bottom edge of the rim of a grand piano, or for a large crack in the back of the top horizontal beam of a vertical piano.
Check legs for cracks or for an undue amount of rocking of the piano.
Check vertical piano for missing casters.
Before lifting the lid, check it for cracks and missing hinges.
Soundboard and ribs
Play all the keys from one end to the other, listening for evenness of tone across the keyboard. Note any buzzing or rattling sounds.
Look for excessive soundboard cracking. More than a few unrepaired cracks in the soundboard may be cause for concern.
Wooden shims in cracks indicate that the piano was rebuilt at some point in the past. Make sure there are no new cracks alongside the shims.
Check to ensure soundboard is glued around the perimeter.
Where ribs cross cracks, check to ensure they are still firmly glued.
Soundboard crown: any measurable crown is good. Some good-sounding pianos have no measurable crown.
Pluck Test: Slowly depress a key in the octave that begins an octave above middle C. This area is the critical “melody range.” While holding the key down (to lift its damper), pluck one of the three strings of the note you’ve chosen. The sound should swell slightly immediately after the pluck and then get softer as the string vibrates. The tone should be clearly audible for at least five seconds. If the sound is less than three seconds in duration, the soundboard may not be functioning properly or the scale may be poorly designed.
Action, Keys, Hammers, Dampers & Regulation
Verify that all keys play. If not, try to determine why. Are some parts missing, broken, or unglued?
Check visually inside, looking for consistent spacing and alignment of action parts.
If made before 1960 and some action parts are plastic, do not buy the piano unless the plastic parts are post-1960 replacement parts (ask your technician).
Visually check condition of hammers, dampers, and other felt parts for moth damage.
Check that all bridle straps (verticals only) are in place and look okay.
Note any sticking or sluggish keys.
Check visually for even spacing and squaring of keys.
Are keytops ivory or plastic? Are any keytops missing, chipped, or damaged?
Check keys for minimal wiggle, rattle, or excessive left-right movement. Are new key bushings needed?
Check hammers for depth of grooves, amount of remaining felt, correct number of string dents, possible wobbly hammers (string dents are misplaced or unclear), loose hammer heads (clicking noise or up/down movement of hammer head).
Play all notes staccato, except those with no dampers (upper 15-20 notes). Do all notes cut off cleanly? If some buzz or continue ringing, dampers may need regulating or replacing.
Make sure dampers move together when right pedal is depressed.
Check condition of action regulation, using visual examples on page 199.
Check repetition on several keys by playing a key rapidly with alternating hands while depressing the right pedal.
Play a number of keys as softly as possible. If the action fails to play reliably (i.e., skips or misses) at reasonably soft dynamic levels, the action probably needs regulating.
Right pedal: see dampers, above.
Middle pedal: If the middle pedal activates a true sostenuto mechanism on a vertical piano, the piano is probably a higher-quality instrument. If the middle pedal does notactivate a sostenuto mechanism on a grand piano, the piano may be a lower-quality instrument. To test the sostenuto: Depress right pedal to lift dampers, then depress middle pedal and keep depressed while releasing right pedal. Dampers should remain raised.
Left pedal: moves hammers closer to strings to quiet the piano (verticals), or shifts keyboard (grands). If left pedal on grand just operates bass dampers, it is often a sign of a lower-quality instrument.
Lost motion compensator (verticals): keeps action in adjustment when soft pedal is used. Usually indicates a better-quality older piano.
Is grand pedal lyre coming apart at the glue joints? Are lyre braces in place and lyre feels secure when pedals are used?
Find the serial number of the piano for later determination of age.
Ask the owner about piano’s history (but take it with a grain of salt).