oliv:

- Can you please post a little more info? What version of PTPA are you using?
How do you want to make "use of an external midi synth? Do you want to record MIDI from the synth to PTPA?

- If you open up the Help file in PTPA, go to the Search tab and type "changes" (no quotes), one of the the entries will be "Setting up the patch changes". See if that's what you're looking for.

- If you can't find anything in the Help file for your "instrument definition" question, check with the Live Help function at the top of most of the PGMusic pages. They can help you with that or get you started.

If you still have questions or issues, post back here and someone should be able to help.

Good luck!
LLOYD S