I think I've heard them, DX but in there, and it's distinctive with the music, and that they have a kind of muffled sound, not crisp. The spectrum display shows the more narrow audio as well, they don't fill up the allotted 10 khz on each side.
You know what I thought? It was a station using a Comrex on the phone, remember those? We had a station that did high school sports from the stadium and sounded like WHLN. They'd go to break and play pop songs, like David Sanborn, and if the board op back at the station wasn't on the ball or didn't have anything to play, you'd hear a few songs through the Comrex.
Booma