Musicians Institute, in collaboration with Revolver Magazine, has joined the Rockstar Energy Mayhem Festival Tour as a co-sponsor. The tour, currently underway, features top metal acts including Slipknot, Disturbed, Dragonforce and Mastodon. At each stop on the California leg of the tour, guitar instructor Greg Harrison (left in photo) has been attracting hordes of excited up-and-coming players by offering impromptu clinics at the MI/Revolver booth. MI Admissions Rep Travis Johnson reported, “Greg was a star at our booth!  He was playing popular, difficult-to-play metal songs and kids’ jaws just hit the ground!” The tour continues through August; stay tuned for more news and video of the Mayhem…