Hi, I am not a piano tech but bought the book by Reblitz and picked up a couple free used piano’s to learn on and to get a good working piano for my grand daughter. I downloaded the tuning program by tune lab, spent a bout a week reading the instructions. I fixed one for my grand daughter and it worked out fine. The next one, a 1949 Kimball consolette was in very bad condition, hadn’t been touched in 15 or more years and mice had filled it up with papers for nests and it had been a house with smokers so smelled pretty bad. I cleaned everything sanded the keys, cleaned and polished the case. Regulated the action (everything was way off) reshaped the hammers then tuned it, it was a whole note off so it took three times to get it right. When it was in the garage I varnished the back and insides to seal the tobacco smell in and let a fan blow on it for 2 weeks. Still smells a little bad. Now if anyone is still reading I have 2 problems I would like opinions on 1) it changes tune between morning and evening, I can’t see how humidity could change that fast so to me it must be temperature. 62 in the am and 70 in the evening, but that doesn’t seem right either any thoughts? 2) Starting at about c up to g In the 3rd octave I get a ringing noise and for a larger area +/- I get a buzzing noise and when the hammer first hits it sounds kind of like hitting the sound board with a rubber hammer. That drum kind of sound. The sound board has about 1/8 inch of crown, no cracks, the bridges are tight with no cracks. I tried removing the wires from the first wound bass polished the point where it hit’s the bridge and twisted them one turn and it made no change. I tried voicing the hammer on that wire which mellowed the sound but made no change in the ringing, I vacuumed the case and blew it out with hi press compressed air. I tried putting pressure on the plate and sound board in different areas while hitting the keys with no change. The dampers seem ok but unable to stop the ringing noise, if I push the damper far enough into the wires so they start spreading them apart the sound will diminish in about 5 seconds but the sound shouldn't be there at all. It seems like almost anything can be repaired if you are willing to put enough time and money in it. I know this piano isn’t really worth the time but this is a learning process so I’m willing to try a lot more just would like some opinions as to where to go next.

PS I confess I am a do It yourselfer, I have repaired microwaves, refrigerators, remodeled houses, built my own kitchen cabinets, painted cars, rebuilt car transmission, rear ends alternators, even rebuilt air conditioner compressors so this is just another challenge I want to try.

Your assessment of pitch change and temperature I believe to be accurate - (but get it out of the garage) - If you put your finger on a plain steel wire for 30 seconds you can hear or measure a pitch change so the steel wire responds fast.
Check the dampers in the area with the drum sound to be certain they are completely clearing the strings when you depress the key. Pluck the strings with a guitar pick so that you can hear the difference between hammer blow and eliminate the hammer. The buzzing/ringing may be a sympathetic ring from other dampers that are not seating properly. Use a towel or something to mute off some bass strings and try to locate a leaker.

There will be some things you can do on a DIY basis in piano work, but some other areas like you have run into with the leaking or ineffective dampers in a Haddit&Howe spinet that will wear you out.

Unlike machinery rebuilding, a piano is a complex interaction of wire, wood, and a little bit of weirdness that can leave the most experienced of us scratching our heads from time-to-time over what they can toss up as problems.

The high-end newer pianos are easier to work on, but there you would probably be better served using an experienced tech. It'll save you time, and the extreme embarrassment of messing up an expensive instrument.

Good luck, but as one who has rebuilt a lot of machinery. I can tell you ... piano work is very different!

Thanks for the responses, I don't have any time untill Sunday but I will try a muting strip on all but one of the wires in that area snd see what happens.