Avant-Prog
Avant-progressive rock is a style of art music based on rock music that explores unconventional territory, often incorporating non-standard chord progressions, tempo changes within a piece, odd time signatures, avant garde passages and complex horn and orchestral arrangements. It generally relates to experimental bands and musicians influenced by 20th century avant garde, classical, jazz, folk and other music, and who stretch the boundaries of the rock form in both the compositional and improvisational arenas.
Often the only similarities between groups creating avant-progressive rock music is their disregard of convention.
History
In the late 1970s a group of European "progressive" bands joined forces under the banner of Rock in Opposition or RIO to unite against the music industry that refused to let their music be heard. While RIO was originally a collective of bands with the same political agenda, the term is now often used to identify the "collective style of music" of the original RIO bands. This "collective style of music" later became known as "avant-progressive rock".
Avant-progressive rock music has since grown beyond Rock in Opposition and now encompasses a far greater body of music than the original "collective music" of RIO.
Source
http://en.wikipedia.org/
