Both jazz and classical music originated in simple dance forms and both have developed these forms into large sophisticated structures. Both musical streams have enriched and influenced each other greatly over the last thirty/forty years.

Third stream represents a merger of classical music and jazz. The term was coined by the great composer Gunther Schuller who is well versed in both classical and jazz idiom to describe music that channelled jazz and classical elements into a new third stream. It combines jazz and classical composition procedures. Modern classical composition is melodically angular and harmonically dissonant. This atonal style first appeared when jazz bands turned to classically trained arrangers. Serial or 12 tone techniques invaded jazz compositions in the 1950's and 1960's. It used orchestral instruments such as cellos, oboes, bassoons and french horns. It imitates classsical music. Avant-garde jazz assimilated the tonal qualities of classical composers such as Wagner, Debussy, Schoenberg and others. Jazz composer borrowed the large extended forms of the Baroque and classicals periods. Some of the outstanding third stream/avant-guarde jazz compositions are: "Transformations" by Gunther Schuller performed at the 1956 Brandeis Jazz festival, "Poems for Brass/Brass Suite" by J.J. Johnson (Who otherwise was a straight jazz composer, but produced this only Third Stream Jazz gem piece), "City of Glass" which is a suite appearing in an LP by the same name in the early fifties, by Bob Graettinger who was a highly introvert serious Third Stream composer, "Mirage" and "Conflict" by Pete Rugolo and other pieces by the Innovations Orchestra of Stan Kenton of the early 50's etc.