This sounds like it would make for a wonderful science experiment. What you would do is measure peoples heart rate while they listened to different songs. It is well-known that different types of music elicit different responses in people. Think about how you feel when you hear classical music. Are you pumped up and is your heart racing (beating very fast) or are you sleepy and has your body slowed down (heart beat lower)? What about when you listen to rock? Based on your own feelings you can come up with what you think will happen to a persons heart rate when listening to the various songs, this is called a hypothesis.

My guess is that it depends on the person.

I'll note that low heart rate does not necessarily mean good. Excitement tends to increase heart rate, as does exercise, and getting exercise is generally beneficial.