It made Pierre Boulez want to vomit: Francis Poulenc thought it was atrocious: and Igor Stravinsky said all you needed to write it was enough manuscript paper. But its composer wrote all 80 minutes of it as a love song, and a hymn to joy. So just what is Olivier Messiaen’s epic Turangalila Symphony, premiered in 1949 by Leonard Bernstein and the Boston Symphony Orchestra, why did it divide opinion so much, and what does it mean today? Producer: Ruth Thomson