Howdy Fred,
Congrats on reaching the NO LATENCY zone
When you say "synchronize a pre-recorded rhythm pattern to match the recording", I'm wondering if you do like I do for some recordings. Do you mean that the first "pre-recorded rhythm pattern" is an audio recording, or a midi recording? I've had both occasions, and I do things quite similarly in both cases. If you don't get it figured out, and you want to give us a few more details (ie, which tracks are audio (if any) and which are midi, etc), then I can tell you what I've done in similar situations. Things may be different, too, if you want to get usable sheet music, or if you just want a performance that you can hear and not worry about the sheet music.
Keep up the good work!
ttfn,
Sherry