CHRIS THILE AND YO-YO MA Two master musicians (plus two more) throw a genre-busting rodeo The rhythmic cascade of Chris Thile’s mandolin kicks off “Attaboy,” the first track of a new album with the unlikely title The Goat Rodeo Sessions. Thile is known for virtuosity and whimsy, so neither the bluegrass chops nor the album title is a surprise. But 32 seconds into “Attaboy,” a deeper-toned, bowed instrument unexpectedly takes the melody....