Bob Dylan asked Mansfield to tour with him on his 1975 "Rolling Thunder Revue" tour. When that tour had ended, Mansfield and two other members of Dylan's band, T-Bone Burnett and Steven Soles, formed The Alpha Band. The band released three albums, The Alpha Band in 1977, Spark In The Dark in 1977, and The Statue Makers of Hollywood in 1978.
Since The Alpha Band broke up, Mansfield has continued to work as a musician in sessions for Dylan, Burnett, Johnny Cash, Nanci Griffith, Bruce Hornsby, Roger McGuinn, Sam Phillips, Mark Heard, The Roches, Edie Brickell, Spinal Tap, Lucinda Williams, Dwight Yoakam and others.