:-)   John, I just knew I couldn't come to a better place for "nice logical hi-tech explanation", thanks to amazing Catters like you! It's going to take me a bit to digest all the various possibilities you've so kindly taken the time to explain -- thank you very much!   

And hey, it's just good to know there ARE so many explanations *whew*

I thought it might have had something to do with "building up the crescendo", that maybe those big chords had overloaded the circuits somehow. But I've played that piano just as loudly countless times before without any problems ... and it doesn't explain what happened to that recording several years ago either.

The difference back then was that the mysterious sounds didn't even present themselves until the next day. It's impossible to dub ANY sounds in over something already recorded on that piano -- if you press REC and play even one note, it erases everything you've recorded before. You certainly can't "insert" new sounds in the middle of a recording, or cause the recording to fade in and out the way it did that morning.   That's why my kids were so freaked (well, me too) ... they were into computers in a big way even back then, and KNEW that what they were hearing was simply impossible.   Weird!

One thing's for sure - I'm not going to be shaking the thing any time soon to check for loose wires. They call it a "portable piano"? Ha! Portable for a couple gorillas maybe ...

At any rate, with all those possibilities in mind I won't be losing any sleep over it. Unless it happens again, in which case further research will DEFINITELY be indicated.

Thanks so much again,

daylia