OH MAN! This is perfect! I went to diagnose the yammy p22 yesterday(I think that's pianotech-ese for yamaha p22). Anyhow, this thing has the exact same "rattle" as the piano I grew up on and am now using in my home.(a studio-kawai-creamy white color) I've been looking for this "snake" since before I knew the reason that funny guy with the bag full o tools came to our house every few years and pounded the crap out of our piano even though I wasn't allowed to pound on the piano. Its a mechanical rattle or buzz. Nothing to do with tuning or hammers not hitting square. Do you know what I mean? It's actuated mostly by notes in the upper third of the piano and I think it may be coming from the fallboard hinge. It stops sometimes. It will do it on loud notes and on soft notes. If I move the fall board a little I can get it to stop. Then, if I leave it for some time and come back, it will come back too. Mysterious, it is. Find it, I must. The owner said, the store tech put something on the ends of the fall board, where it attaches to the case or frame. I looked,...on the pin with the little locking flange there seemed to be an extra washer or maybe even a balance rail felt to keep things from rattling..... Not helping. Is there a possibility we would need to get a better quality hinge?. I think its the long skinny pin going through the center of that hinge. or still something to do with those locking flanges, whatever they're called.
feel free to comment it you like!