Mountain Grass Unit is the bluegrass band to know right now. Mountain Grass Unit is the hottest band in bluegrass right now. Westword first discovered Mountain Grass Unit at Telluride, where the band’s refreshing jamgrass caught the attention of Rolling Stone, too. “They’re so good.”Over the past year, Mountain Grass Unit shows have become more and more packed out. Courtesy Mountain Grass UnitMountain Grass Unit is cruising from Illinois to Iowa on an off day when Westword checks in.