From the liner notes

Unwigged & Unplugged has two plus hours of songs from the legendary musical and comedic trio, Christopher Guest, Michael McKean and Harry Shearer, performing music from heavy metal's loudest band Spinal Tap along with folk music from A Mighty Wind, and more. Unwigged & Unplugged is not about funny costumes and characters, but rather three long time friends and collaborators finding an excuse to get together and play music. Falling on the 25th anniversary of the film This Is Spinal Tap, this is the first time the guys have performed as themselves.