Piano repair is not a DIY project. There are some things better left in the hands of trained specialists, and brain surgery and piano repair are the two top ones in my opinion. Notwithstanding the fact that I am guilty as a child of rubber banding some felts that were being obstinate, and gluing a shiv onto a hammer that simply could not reach far enough any more. Do as I preach, not as I did as a classical loving 12 year old.
If a piano is well protected from vermin and humidity, there is no reason an elder piano cannot be refurbished to have better sound and tone than it did when new. The sound board is the foundation of the piano, and if the soundboard is cracked, warped or distressed, the rods will not move correctly, the felts and hammers will get incorrect messages or none at all. The results will be a buzzing slightly when depressing certain keys, or again, no sound at all. The worse sound for most people is a piano out of tune, but that is a natural event not cause for piano repair. If the sour notes are not due to hidden disabilities good tuning can be remedied by a professional piano tuner in approximately two hours time. In the past, piano tuning was so respected the tuner signed and dated inside the instrument each time he tuned it. It was a matter of pride and respect for the piano, the tuner, and the musician.
Bridge and Pinblock Examination
The bridge is a wooden piece between the soundboard and the hammers, helping to maintain the piano in tune for reasonable time. This wooden piece should not be out of position, warped or cracked. The pinblock holds each string ensemble with tuning pins. The pinblock must not be cracked or splintered at all, and tuning pins must be tight. The piano strings are attached in groups or two or three, and if this pinblock system is damaged, the piano will remain out of tune. If you see signs of rusting anywhere, strings, pins, wherever, it probably would cost more to have it refurbished than it is worth. You would need the advice of a trusted piano repair specialist.
Hammers Inspected for Wear
Each hammer in a piano is covered in felt. Timbre is achieved by the hammerhead felts being struck against the strings to produce the desired note. Worn felt sacrifices timbre and tone. Make sure no wood is exposed through the felt. Play each key, and listen for a harsh tone, particularly in treble octaves. Hammer felt is attached to the hammer by tons of pressure, not glue. (As I learned as a child.)
Check the Keys
The keys should be checked by playing them and listening closely. The tuning may be off but you should listen for buzzing sounds or harsh multi-tones even though one key is depressed. If you have has the foresight to have a piano repair technician accompany you in your shopping, this is time to let him or her lead the dance. He could save you wasting money or assist you in buying an outstanding instrument.
Piano pedals that are unresponsive can be big or little problem. They need to provide clean tones. You don’t plan on using the pedals? Examine and test them anyway, because if they are not working easily and well, they could be indications of other problems inside the piano.
Refresh your memory on what humidity, harsh weather changes and too little protection will do to the insides of the piano. Look at the cabinet housing the valuables for any blemishes such as weathering, dampness or even long periods of heat and bright sunlight. If they are present, the piano is most likely permanently disabled and not one of the ones mentioned in the second paragraph which can be refurbished and sound better now than when new.