Trust me, sir; If I'm misleading it's strictly out of ignorance!!! I convinced my friend to buy Reaper and an interface. He sent me a file (MP3) with a single track featuring vocals with guitar. I added some tracks and sent it back but when he opened it, though the tracks were there, each one had "offline" in the space where the audio should have been. So, I went back and changed the file type to MP3 (which I thought it was already, but it wasn't) and resent it. Same result. Neither he nor I have done this before so we're kind of in the dark.