CB repeaters are frowned upon, but I've heard two or three in the field.
In practice, background music is commonplace on CB due to everyone listening to the radio or whathaveyou while talking. Here in the Chicago area, I've heard music straight from CDs, guitar solos from passengers, morse code, and more over CB. Don't take my word as gospel on this, but considering how music is handled in Afternow, it shouldn't be anything out of the ordinary compared to normal broadcasts. Just avoid channels people are trying to talk on, and channels reserved for emergencies.
The cardinal rule is "Don't be a nuisance."
yep, tis true...also the FCC doesnt stray over into the CB area very much so you can pretty much do anything that you want as long as you are not on channels 17, 19 and 9 (US only)
