Three years ago, Mark Tremonti — guitarist/singer-songwriter/founding member of the rock bands Creed, Alter Bridge, and Tremonti — became absolutely obsessed with Frank Sinatra. Though he’d always been a fan of Frank’s and sang along suitably with Sinatra’s low register, this time was different. It was as if Tremonti was being deliberately pulled in Sinatra’s direction. Tremonti watched movies, read books, and insatiably scoured Sinatra’s catalog. He sang his songs relentlessly, even teaching himself to breathe, enunciate, and inflect like the legend. But still, even after 18 months, Tremonti couldn’t quite identify the reason for his newfound passion. Then it happened: Tremonti’s daughter, Stella, was diagnosed with Down Syndrome. Today, Tremonti is temporarily trading in his hard-rock se...