Sometimes, they could use a traffic cop inside KVMR’s downtown Nevada City studios on Saturday afternoons. The program featured live performances by Sacramento-turned-Austin folksinger Bob Cheevers, the local female roots trio the Heifer Belles, and Joe Craven and Painted Mandolin, a side project fueled by Jerry Garcia’s acoustic music. “I have this love to send live music out on the airwaves,” explained Robertson. “The amount of room we have in here is such a help, and people tell me the live music sounds like a CD or a studio recording, not live music.”Plus there’s often a comraderie among the artists. YARN LIVE FRIDAY NIGHTThe acclaimed jam band Yarn returns to the Crazy Horse for a live broadcast on KVMR this Friday night at 9:30 p.m.Only with one big wrinkle.