Some of my loops are pre-recorded to save some time or to use equipment I don’t bring to every gig. I recorded my loop with the BB running in the background. After recording, I checked the tempo of my loop. It was .2 or so off…I just went in and adjusted the RC-300 tempo to match the BB exactly. It wasn’t a big enough adjustment to notice any stretch or squish on the loop, and it keeps time perfectly.
There is a way to set the tempo of the RC-300 on a blank program. If I remember correctly, you have to record a loop at the tempo you want—use the RC-300 drum sounds. Then copy that song to another channel. Then you can delete the loop, write to that channel again, and it should have saved your tempo for you.
Also… I think someone mentioned you can use the RC-300 drums at your fixed tempo, but just turn the drum sound down to 0.