1.) Make sure every key works by pressing the key down and releasing. If you hear a sizzle or metallic sound When you release the key the damper felt has hardened. If the tone is bright and metallic as well the hammers need to be replaced. If keys aren't working call in a pro to assess the situation. With over 6,000 moving parts in a piano there are many possible reasons for sticky keys, dead notes, double striking, etc...
2.) Check the back of an upright or underneath a grand piano for cracks in the soundboard. If you suspect something that looks like a crack but you aren't sure, run the tip of your finger across it. If you feel a ridge this can eventually lead to separation.
3.) Check to see if all pedals are working - Do all the dampers lift simultaneously with the sustain pedal? Operation of the middle pedal can vary. Full sostenuto or a bass damper lift in grands. Full Sostenuto or practice pedal in uprights. Left (Una Corda) pedal on a grand should shift the action so the hammer contacts less strings creating a softer sound. Uprights have a soft pedal that brings the hammers closer to the strings with similar effects.
4.) Ask for service history. If it is extremely out of tune, especially unisons, you will need to have a professional come in to check tuning pin tightness. The pinblock could have cracks or contamination that make the piano un-tunable.
5.) Make sure you fall in love with it completely. Good advice when buying any instrument but more so with a used piano. There is usually no trade-up policy, manufacture warranty, or returns when purchasing a used instrument. Know what your preference is and don't "settle" because of price. For example, you can't make a small piano look or sound like a big piano. Being content and happy with your investment will ensure you enjoy playing and learning.
Joseph Raville, RPT
Dallas Piano Tuner
Up to Pitch LLC
469-554-8863
joseph@uptopitch.services