This is extracted from http://www.jneurosci.org/content/23/27/9240.
Participants showed off their brains in a battle concerning grey matter: who had more, musicians or non-musicians?
Professional musicians (full-time performers, teachers, or conservatory students who practiced more than 1 hour a day), of course. Amatuer musicians (people who played for pleasure) were found between the two.
Here’s a graph displaying different angles of the brain, with the advantage of music shown in red: