UNDERTURE

'"Underture"' is the tenth song on The Who's 1969 rock opera, Tommy. Written by Pete Townsend, it is a lengthy instrumental representing the protagonist of the rock opera, Tommy Walker's experience on acid after visiting the Acid Queen. It is often considered the second part of "Acid Queen".
The musical theme is the same as in the second part of "Sparks" and was originally a part of The Who's mini-opera "Rael", from ''The Who Sell Out'' (1967).
The original name for this song was "Dream (Psychedelic)" because it represents Tommy's acid-induced hallucinations.