I also have an external speaker rigged to the bike. It does not have a power source so the sound is tinny and quiet, but it's perfect because when the traffic is high and I need to really pay attention, I don't hear it. When i'm on the quiet backroads, it comes through loud enough that I can sing along. I like to sing when I ride, and my speaker setup doesn't afford much bass, so I tend to stick with melodic folk, blues and pop. I love Eva Cassady for the fall, Iron and Wine, and Kings of Convenience. Not very motivating for fast paced riding, but seasonally appropriate. Once the winter really sets in, I will probably listen to a lot of Tool and A Perfect Circle. Tough music for tough rides.