The actors teamed up to create a new version of Little Drummer Boy for the holiday season.
And their effort has been turned into a cartoon.
Black, who plays Lemuel Gulliver in a new movie adaptation of the classic Jonathan Swift novel, showed it off during an appearance on The Tonight Show with Jay Leno on Tuesday night.
"This old chestnut was dying to be rockified ... enjoy," Black said of the cover version, which is backed by their interpretation of Peace on Earth.
All proceeds from sales will go to benefit Blue Star Families, a charity that helps needy military families.
Billy Connolly also appears in Gulliver's Travels, which hits cinemas in the US on December 25 and in the UK the following day.