"O" is the third studio album from the orchestral rock group The Flowers of Hell. It consists of one song lasting 46 minutes in its stereo mix and 42 minutes in its surround sound mix. The release's liner notes state that the piece is an exploration of band leader Greg Jarvis's synesthesia and was conceived as a piece of absolute music. It consists of rehearsed improvisations performed with-in a 12 part fixed song structure, recorded in one take at the end of a 9000 km tour. In a 2010 interview with Spinner, Jarvis said that "O" was also designed to explore music's unique capabilities as an art form that unfolds over time.