I tried to listen to my iPod once while I was riding! That lasted all of ... 20 seconds? It's really weird having music playing and eliminated the normal things I'd hear, like my horse's breathing / snorts, hoofbeats, stuff like that. It really made me realize how attentive to sound I am when I ride. As far as playing on a boombox or over a speaker or something... no I've never done that. I think some people in freestyle dressage have it very well coordinated! I heard Ms van Grunsven actually writes the music herself and calibrates it to her horse's movement. Stunning thought!