Unit 4 was later joined by Russ Ballard on guitar and Robert 'Bob' Henrit on drums (forming the + 2) for a six piece, four-part vocal harmony group. Moeller was lead singer and front man from the first show as the Unit 4 vocal group to the last show as Unit 4 + 2 as vocal group with instruments. Due to ill-health and a dislike of performing live, Brian Parker left the band, but remained involved as co-songwriter with Tommy Moeller for all of the band's original recordings. His place at live performances was taken by Howard 'Lem' Lubin. Around 1967 when they recorded their second album, Rodney Garwood replaced Peter Moules on bass (who had taken up bass when the band changed from a vocal group to a pop band) and Hugh Halliday replaced Bob Henrit.