Nice story.

I had a CN33 for a couple of years that annoyed me with a buzzing low note. I suspected a resonance but could never track it down. When it came to selling the CN33 I moved it to another room ready for its replacement, and was amazed the buzzy note was gone.

With the new DP I tracked the buzz down to a wall mounted clock. I think this sort of problem and investigation is standard fare for piano tuners and technicians.