Barrett had guest vocals on the Street Dogs song "Justifiable Fisticuffs" from their first album "Savin Hill", on The Gaslight Anthem song "The Patient Ferris Wheel" from their album "The '59 Sound", on "Charge into The Sun" from The Briggs' album "Come All You Madmen", on The Unseen's cover of "Paint It Black" from the album "State of Discontent", and also on H2O songs "Force Field" and "Faster Than The World" from their 1999 album "F.T.T.W.", as well as Rancid's songs "Cash, Culture and Violence" and "Black Lung" on their album "Life Won't Wait". He also made guest appearances on tracks from No Use For A Name, Clowns For Progress, the Stubborn All-Stars, and local Boston band Darkbuster.