Yes - Gates of Delirium 

"The Gates of Delirium" is a song by the English progressive rock band Yes, recorded for their seventh studio album, Relayer. At almost 22 minutes in length, the song is loosely based on the 1869 novel War and Peace by Leo Tolstoy which originated from a musical idea that frontman Jon Anderson had that depicted a battle. It was then developed and arranged into a complete track by Anderson and the rest of the band, namely bassist Chris Squire, guitarist Steve Howe, drummer Alan White, and keyboardist Patrick Moraz. Musically, the song represents an introductory vocal section followed by an instrumental that represents the battle. The final section, entitled "Soon", is a gentle, soothing prayer for peace and hope.