Rock in Opposition or RIO was a movement representing a collective of progressive bands in the late 1970s united in their opposition to the music industry that refused to recognise their music. It was initiated by Henry Cow in March 1978 when they invited four European groups to come to London and perform in a festival called "Rock in Opposition". The bands in the R.I.O. movement were also described as "avant-progressive rock" or "avant-prog". Other bands include Art Bears, Univers Zero, Etron Fou Leloublan, Samla Mammas Manna, Stormy Six, Art Zoyd and others.