Progressive rock (sometimes shortened to "prog rock" or "prog", also called "art rock") is a form of rock music that evolved in the late 1960s and early 1970s, as part of a "mostly British attempt to elevate rock music to new levels of artistic credibility".
Progressive rock bands pushed "rock's technical and compositional boundaries" by going beyond the standard rock or popular verse-chorus based song structures. As well, the arrangements often incorporate elements drawn from classical, jazz and avant-garde music. Songs with lyrics are sometimes conceptual, abstract, or based in fantasy. Progressive rock bands used "concept albums that made unified statements, usually telling an epic story or tackling a grand overarching theme".
The band is noted for their musical diversity, multi-layered arrangements, vocal harmonies, and incorporation of audience participation into their live performances. Their 1985 Live Aid performance was voted the best live rock performance of all time in an industry poll.
Queen enjoyed success in the UK in the early 1970s with the albums Queen and Queen II, but it was with the release of Sheer Heart Attack in 1974 and A Night at the Opera the following year that the band gained international success. They have released fifteen studio albums, five live albums, and numerous compilation albums. Eighteen of these have reached number one on charts around the world. The actual figure of Queen's album sales varies by source, generally ranging from 100 - 300 million albums sold worldwide. According to an interview transcript on Brian May's official website, the band had sold in excess of 190 million albums by 2006.
Following Mercury's death in 1991 and Deacon's retirement in 1997, May and Taylor have performed infrequently under the Queen name. Since 2005 they have been collaborating with Paul Rodgers, under the moniker Queen + Paul Rodgers.