Third stream is a music genre that is a fusion of jazz and classical music. The term was coined in 1957 by composer Gunther Schuller in a lecture at Brandeis University. There are many ways to define third-stream music. It could refer to a group of jazz musicians playing solely, or a jazz soloist performing with a symphony orchestra, as long as the musicians are able to interpret and play jazz music. Improvisation is generally seen as a vital component of third stream. In third-stream music, composers incorporated elements of classical music, such as the use of jazz instruments and classical music forms, into their jazz compositions. The fusion of jazz and classical music is also viewed as "born out of a reciprocal interest: the interest of the classical community in the developments in jazz music and the interest of the jazz community in the advances of classical music." The innovative idea of fusing jazz and classical music pushed the boundaries of traditional classical music and introduced a new genre that blends the two styles into a unique hybrid form.

J. J. Johnson, born James Louis Johnson and also known as Jay Jay Johnson, was an American jazz trombonist, composer and arranger.