<em>-By Dave Stallard</em> Once upon a generation, an instrumentalist will redefine his instrument through sheer ingenuity and virtuosity. Think of Jimi Hendrix’s electric guitar, Earl Scruggs’s three-finger banjo roll, or even Jerry Lee Lewis’s piano ministrations. For mandolin enthusiasts, David Grisman and Chris Thile have reached such iconic status. Both are rooted in bluegrass, but Grisman and Thile have allowed their musical imaginations to wander the world in search of inspiration. In doing so, the role of the mandolin in contemporary acoustic music has blossomed. Grateful Dead fans were introduced to Grisman through his collaboration with Jerry Garcia in Old and in the Way, arguably the first band to bring bluegrass to rock ‘n’ roll fans. For the last 30 years, Grisman has blended bluegrass with gypsy, jazz, swing, and Latin music to create “dawg music,” a genre appropriately named after the nickname of its originator. The David Grisman Quintet recently released “Dawg’s Groove,” the latest chapter of their jazzy stylings. The disc opens with “Limestones,” where Grisman’s mandolin trades blistering lead runs with Matt Eakle’s flute. “Blues for Vassar,” a lament for the recently passed fiddling legend Vassar Clements, closes the album and is a fitting tribute to Grisman’s musical compatriot. It seems that Chris Thile has been playing his mandolin forever. He released his first album at 12, and his work with Nickel Creek has kept him in the spotlight for much of the last decade. Nickel Creek’s impending hiatus, though, could give Thile the opportunity to create his finest music to date. He recently released “How to Grow a Woman From the Ground,” a stunning collection of grass-rooted originals and covers. Thile’s interpretations of progressive rock tunes like The White Stripes’ “Dead Leaves and Dirty Ground” or The Strokes’ “Heart in a Cage” will surely turn heads, while the band will also impress on more traditional tunes like Thile’s “Watch ‘at Breakdown” and their rendition of David Rawlings and Gillian Welch’s “Wayside (Back in Time).” Constant evolution keeps music interesting and fresh. Grisman and Thile’s recent releases prove that they are doing their part to push the boundaries of acoustic music.