"Did you know that every time musicians pick up their instruments, there are fireworks going off all over their brain?"
That's the launching point for a fantastic little video made by educator Anita Collins and animator Sharon Colman Graham for TED-Ed. What they explain is that while listening to music is beneficial, playing music is "the brain's equivalent of a full-body workout."
https://www.youtube.com/watch?v=R0JKCYZ8hng#t=19
What's more: Neuroscientists have found that some of these aspects of mental work are different from any other activity studied, including playing sports or engaging in various creative pursuits.