The Four Seasons (known off and on since 1967 as Frankie Valli & The Four Seasons), are an American pop and rock group, distinct from many similar groups of the early to mid-1960s in its traditional Italian-American sound. It also had a sound somewhat reminiscent of doo wop, but it was not known as a doo wop quartet. By the mid 1960s it had become an internationally famous rock and roll group. In 1960, the group known as The Four Lovers evolved into The Four Seasons, with Frankie Valli as the lead singer, Bob Gaudio (formerly of The Royal Teens) on keyboards and tenor vocals, Tommy DeVito on lead guitar and baritone vocals and Nick Massi on bass guitar and bass vocals (Massi was replaced in 1965 by Charles Calello, who was in turn replaced in 1965 by Joe Long on bass guitar and bass vocals).