For people marveling at the first-class entertainers who have played in Manchester for the Bonnaroo Music Festival, McMinnville isn’t far behind.“Bluegrass Underground” filmed its second TV season at Cumberland Caverns over the weekend with performers such as Vince Gill, The Civil Wars, Doyle Lawson & Quicksilver, and Del McCoury taking the stage. This is after Ricky Scaggs headlined last year’s inaugural TV series for PBS.“We didn’t know it would be this fast, but we always figured we’d get to this point,” said producer Todd Jarrell. “We want Cumberland Caverns to be known like a Carnegie Hall, as a place where you have to perform during your music career.