A Whiter Shade of Pale.

Structurally and thematically, this song is unusual in many respects. While the recorded version is 4:03 long, it is composed of only two verses, each with chorus. The piece is also more instrument-driven than most songs of the period, and with a much looser rhyme scheme. Its unusually allusive and referential lyrics are much more complex than most lyrics of the time (for example, the chorus focuses on Chaucer's "The Miller's Tale"). Thus, this piece can be considered an early example of progressive rock.