"Steppin'" -- 1981
World Saxophone Quartet 

Hamiet Bluiett: Alto flute
Julius Hemphill and Oliver Lake: Soprano Sax
David Murray: Bass clarinet

In this performance the improvised section stand out from the main theme which is clearly arranged.  The group improvisation (collective) is one of the groups strongest attributes.  Notice how the texture of the arranged sections which open and close this performance is maintained to some degree throughout the improvised section.