We've received a question, "does the recording have to be all parts live or can the different parts be recorded and then mixed together?"
Answer: it is permissible to record the parts separately and then mix them together afterward. It isn't required, however. The goal is to produce the most convincing rendition of the song, however you can best do that. The judging process will take into account the different recording processes used, so if you do produce a recording of a live performance where there is no post-production (mixing, etc.), you won't necessarily be given negative scoring points if there are a few minor glitches here and there.