It makes them more efficient at solving problems. So is it bad to benefit the brain? For the reason I said I think it is benefit's the brain. It also will make them more likely to pay attention and learn. I'm going to play my violin right now thank you.
I can see how listening to music can be relaxing. However that is still up to the individual. I see no connection to playing an instrument and mental ability or success in life. I personally have zero musical skills but that does not affect anything else. Anyone who knows about multiple intelligences would agree that playing music is not suitable for everyone and should never be required. That would actually hurt all students involved.
Yes, playing an instrument would be fun to play, however it should not be required to have to learn to play one in school. The same thing goes with being on a sports team. That's suppose to be for people who are active in sports. Band, orchestra, and choir should be open to musically talented students, but not required.