Doc Severinsen has parlayed his job as a trumpeter and band leader for the Tonight Show Band into a lucrative career of nightclub appearances in Las Vegas and around the country. But his playing on television has also landed him, indirectly, a gig with the McLean Orchestra.

Col. Arnald Gabriel, music director for the community orchestra, became acquainted with the flamboyant musician more than 25 years ago, when Severinsen was playing for the "Tonight Show" in New York and Gabriel was with the Air Force Academy's music program. "I remember hearing this unusually brilliant soloist playing in the section on television," Gabriel recalled.

Gabriel had Floyd Werle, the Air Force Band's composer and arranger, write a trumpet concerto for Severinsen that would exploit the now popular trumpeter's vibrant style, blending classical and popular idioms. Severinsen will play Werle's concerto when he joins his old friend Gabriel on stage again April 2 at Langley High School in McLean.

Gabriel leads the 65-member McLean Orchestra for the second year, adding very few new musicians to a group that he built practically from scratch last year. The group will play five concerts beginning Oct. 24 at McLean High School, with a program of Russian music, including Rachmaninoff's 2nd piano concerto, played by University of Maryland pianist Glenn Sales.

On Nov. 1, the orchestra will host its annual tea dance fund-raiser at the Sheraton Tysons Corner. The orchestra will hold a free pops concert Father's Day at the McLean Hilton.

The orchestra will present a Christmas concert Dec. 5, at Langley High School. WGMS radio personality Renee Chaney, who is Gabriel's wife, will narrate "The Littlest Angel," while Bob Ryan of WRC-TV will narrate the Christmas story according to St. Luke.

In February the orchestra will perform a children's concert at Langley High School.

And in May Italian music will be featured in a concert at McLean High School, with Verdi's seldom-heard "Te Deum," with the participation of the choirs of the Andrew Chapel United Methodist Church and the Falls Church Presbyterian Church.

Information for the upcoming season can be obtained by calling Sharon Moore, orchestra general manager, at its new McLean office. The telephone number is 893-8646.