"Third-stream music" is a term applied to the convergence of certain jazz and classical concepts and techniques. A leading advocate of this convergence has been Gunther Schuller, who has played with the Metropolitan Opera Orchestra and the Miles Davis Nonet. Schuller tested his theories last night at Wolf Trap as he conducted the National Symphony Orchestra with guest appearances by jazz artists Sarah Vaughan, Adam Makowicz and the Medium Rare Big Band.

The potential and obstacles inherent in third stream fusion were apparent in Schuller's arrangement of four Duke Ellington pieces from 1933-40. The orchestra brought out the rich tonal colors in Ellington's writing as never before. Particularly striking was the glowing resonance of the woodwinds on "Azure," yet a price was paid, as the irresistible Ellington swing evaporated.

The orchestra's soloists mostly kept their eyes glued to the sheet music, and improvisation was as scarce as swing. The mixture of rich tone and scant freedom persisted throughout the orchestra's opening set, making the third stream much more classical than jazzy.

Polish pianist Adam Makowicz was classically trained in Krakow before falling in love with American jazz. Thus he was a natural for a third stream concert. He soloed during George Gershwin's "Rhapsody in Blue" and added an original cadenza of his own. His solos were showcases for his virtuoso technique as his left hand danced below and above his repeating right hand figures.But his playing lacked the rhythm and feeling he'd shown with his own band at Blues Alley.

It took "the Divine One," Sarah Vaughan, to restore some swing and sass to the concert. She made the second set all her own, swinging the evening's pendulum far over to the jazz side. She sang basically the same show 10 days earlier at the Merriweather Post Pavilion. The National Symphony Orchestra was a lot more powerful than the big band that backed her in Maryland. But it hardly mattered, for Vaughan was 90 percent of the show, and her own trio was another 7 percent.