When I can't ride outside I spin at the gym. Have been doing this for almost 4 years and have gotten pretty good at getting a decent workout whether it's intervals or endurance/cadence drills. I don't know about your instructor, but I've gotten to be good friends with mine and they don't care that I bring my own playlist on my ipod. If I couldn't spin to my own music I couldn't do it. Some instructors may get upset about this -- if so, then sit in the back. You don't have to do their ride unless it works for you. Being with a group of people is also a bonus.