"Spinal Tap" star and mockumentary director Christopher Guest is working on a television project, reports New York Magazine’s Vulture blog.

Guest, who played Nigel Tufnel in 1984’s "This Is Spinal Tap," is working with his British cohort Jim Piddock, who co-starred in Guest’s "Best in Show" and "A Mighty Wind," the story says.

The project is said to be an improvised genealogy comedy called "Family Tree," which tracks "Bridesmaids" star Chris O’Dowd as he investigates his real family, the story says.

Guest and Piddock want the half-hour show to be commercial-free and improvised, along the lines of "Curb Your Enthusiasm." NBC Universal International Television is shopping the project to pay-TV and streaming services such as HBO and Netflix.

Guest is also known for directing the features "Waiting for Guffman" and "For Your Consideration."