Freewheeling cross-cultural experimental balladeers Sui Generis are considered one of the most influential bands in the history of Argentinian rock music. Formed in the late-'60s through the merging of two pre-existing groups, they drew on a range of American and British genres that were popular during the period—including psychedelia, progressive rock and folk. But while their career might have been short-lived (the group broke up in 1975), they have been known to surprise audiences with public reappearances over the years.