This one goes out to all the guitar nerds in the house. It’s also for the Wilco fans, the jazzers, the gearheads, the experimental-music geeks and the noise-rockers among us. Such is the diverse appeal of Nels Cline, the preposterously skillful and adaptable guitarist’s guitarist. To most, Cline is known as the guy who shreds nasty solos in those bright red pants on stage with Wilco. But he’s also a big part of the underground rock and free-jazz scenes making challenging and expressive music with countless artists, including those in his current band, The Nels Cline Singers.