Chaplin initially attracted attention as a member of the Flames, a soul cover band that became the first non-white group to reach the top slot on South Africa's music charts with their 1968 single, "For Your Precious Love." The following year, the band's performance in a London club was overheard by Carl Wilson of the Beach Boys. In search of bands to produce for the Beach Boys' label, Brother Records, Wilson invited the band to record in Los Angeles. In addition to changing their name to "the Flame" and producing their debut album, Wilson had the group open shows for the Beach Boys in 1970 and 1971. When the Flame disbanded in 1972, Chaplin and drummer/percussionist Ricky Fataar were invited to become full-time members of the Beach Boys. The two musicians remained with the band until 1976, helping to record three albums -- Carl and the Passions: So Tough, Holland, and Live in Concert.

After leaving the Beach Boys, Chaplin began working with Dave Mason, Joe Walsh, the Band's Garth Hudson, and Rick Danko and participated in an early-'80s reunion by the Byrds. He recorded a self-titled debut album in 1977 with Hudson playing accordion on one track, "Riverboat Queen." Chaplin's second solo album, Skollie, recorded with Keith Lentin and Bryan Miller, was released in 1992.

Following the death of the Band's pianist/drummer/vocalist Richard Manuel in 1986, Chaplin was recruited to play guitar and drums and to sing Manuel's vocal parts. Although he only remained with the group for one year, he returned to play on their 1996 album, High on the Hog. The following year, Chaplin played piano and bass on the Rolling Stones' album, Bridges to Babylon.