Often times, at least I know in the gym that I work in, the people working out decide on the music. That is a great thing unless, someone else is there first or you are really unassertive and would never touch the stereo anyway. So, brining your mp3 or ipod is a great plan to account for this. I have even seen people that have a book or something recorded on to theirs and listen to it. They only caution I give with that is to make sure the focus in on working out still and not on the book.