In 1967-1968 some Swedish avant-garde poets, artists, critics and musicians turned to pop music and formed groups that performed at museums, happenings, art galleries and other venues. Blå Tåget often used a variety of genres, sometimes with a nostalgic or ironic perspective; Träd Gräs & Stenar produced a mixture of rock, Swedish folk fiddling and minimalist drones and riffs. After 1968 both groups expressed a critical perspective on Western society and capitalism, and became leaders in building "the progressive music movement", which during the 1970s was a strong alternative force in Swedish music alongside subsidised art music institutions and the commercial music industry.