Although some of the 1960s bands performed covers of songs by hard rock pioneers like Cream and Jimi Hendrix Experience, hard rock gained large popularity in the early 1970s with the works of progressive rock bands Pop Mašina, YU Grupa and Smak. Pop Mašina, formed in 1971, was one of the first Serbian and Yugoslav bands to move away from rhythm and blues towards harder sound. Their sound featured progressive, hard, psychedelic and acid rock elements. Pop Mašina disbanded in 1977. YU Grupa, formed in 1970, performed progressive/hard rock, and their songs often featured traditional music elements. The band disbanded in 1981, only to reunite in 1987. Since their comeback album, "Od zlata jabuka" (1987), their work has been mostly hard rock-oriented. Smak, formed in 1971, performed jazz-influenced progressive rock, but their sound often featured hard rock, blues and folk elements. The band moved towards more commercial hard rock at the beginning of the 1980s with the album "Rock cirkus", but the album saw little success and the band disbanded shortly after, having constant reunions disbandments throughout the 1980s and 1990s.