Thanks for the great ideas.

My piano was set to transmit on channel 1. I changed it to transmit on channel 4. Same problem.

WRT the question of what other midi info might be being trasmitting, I realized that the sustain pedal also transmits, so I tried recording with no pedal. Same problem.

Also, I tried playing the file back, viewing the pianoroll display with the channel set to various numbers. I don't see any data on the other channels.

Midi thru has been off in all cases.

No paydirt yet, but these were all good ideas, for which I thank you all.

One more piece of data: If I record a longer piece, more of those lines accumulate. After several minutes of recording, there may be 5 or 6 lines. I take this to be consistent with the idea that notes are getting turned on, then left on instead of turning off.

Any more thoughts?

Thanks again.

Ed