I haven't seen this addressed anywhere yet and I'm too impatient for the official Harmonix documentation! I have a few songs in the pipeline for RBN, super excited to get started!
Would I be importing literally every track into Reaper? For example, background vocals and rhythm guitar during a solo which aren't actual gameplay tracks. Would I keep these as separate tracks or will I need to mix one track that contains all of the extra music that isn't played or sang? So there would be, vocal track, guitar track, bass track, drum track and miscellaneous track with background vox, rhythm guitar, piano, etc. Anyone know?