I have Roland HP 203 piano but I think that it will apply for all (or most of) Roland pianos. I have some recordings of my playing using the piano sound and I wanted to edit it to use harpsichord sound instead. I've created two test recordings, one using piano and the second one using harpsichord sound to see what's the difference between the two. I realized that the difference is the "patch number" parameter so I changed that parameter to "Harpsichord" in my piano recordings. The thing is that the piano replayed edited files with harpischord sound but not the nice one with key-off samples but some other harpsichord sound that doesn't sound as good. If I record midi file using the "nice harpsichord", import it to my midi sekvencer and export it without any change, the piano doesn't replay the track with right harpsichord sound. I assume that it uses harpsichord from standard MIDI set of instruments. Obviously MIDI sekvencer leaves something out during import export. My question is: Does anyone knows what is it? What parameter must be set in midi file to instruct Roland pianos to use instrument which is normally accessible through instrument buttons (in case of HP 203).

There's the "general midi" set of patches.
THEN, there's the roland specific "GS" set of patches.

You probably have to pick the right BANK in addition to program change for that harpsichord sound.
cc#0 is bank MSB and cc#32 is bank LSB (i think? - verify that),
and there's program change.

Look in your manual for which bankhi, banklo, progch #s you need to send to pick it.
Or maybe set your sequencer to record,
pick the sound via the piano console,
then see what programchange,bankselect-high,bankselect-low got recorded?
this MIGHT help... http://pianocheater.com/midi

Steven, thanks for your reply, it was very helpful. It just needed to select right bank just like you said. If anyone is interested: To use harpsichord sound on Roland HP 203 (the one accessible through "Piano" instrument button) you have to select this bank: MSB=0, LSB=66 and use patch number 7. For the reference on other sounds get the HP 203 MIDI implementation manual at here.