Music can move people. Music is super emotional. We associate time, events, places, and people with songs or albums. Music is used for many things, and one of my favorite uses is adrenaline boosting during workouts, jogs, and long road trips. Music makes the gym easier to endure.
The MP3 player has made people much more powerful with how they consume music and what they consume. This is incredibly important at the gym. Now people are not at the mercy of the gym speakers because of an 8 oz player on their arm. CD players skipped (I had a discman sport), tapes were poor quality and wore out, but the mp3 player puts the power in your hands for a personalized workout with little physical interference.
This does kill some comedy though at the gym. At gyms at my college, and there were 6 or 7, the music was all CD based. The employees at the time controlled what was playing. Some rocked out to 80s tunes, Guns n Roses, alt rock, and top 40. The best though were the off times you'd go and catch someone dancing to their own terrible music. A young male dancing to Pink's "Get the Party Started" with his arms above his head like no one was watching will forever stick in my mind. It was a 10am Saturday workout, and the 4 people at the gym were too tired to laugh at the guy. My favorite employee at any gym ever was the bald guy at the North Campus gym who played early 60s tunes and the B-52s. Shit you not, after "red rubber ball" and "feelin groovy" you'd wait for the CD change and hear: "there's a lot of ruins in Meso-po-ta-me-a". He'd put it on random to mix it up, but who in their right mind could stay focused when "Rock Lobster" was blasting.
Music gets me and some others I know through life. I work out to keep my body healthy, my mind free of internalized stress and body looking sexy, but it is a chore. Music keeps me focused. The mp3 revolution allows me to control what I listen to and when I listen to it. This is a hidden gem of the change in modern music. Sure no one buys albums for the albums anymore, but the power is in the hands of the consumer in how they want to interact with their music.