The flair of the Canadian Brass and the elegance of guest conductor Isaiah Jackson turned a rather curious mixture into a highly successful National Symphony program at Wolf Trap last night.

The first part of the evening belonged to the five gentlemen from north of the border. After a couple of precise but prim opening numbers from the orchestra, they walked on stage with their gleaming instruments in hand. Dressed in pale blue summer tails with matching bow-ties, they lined up on yellow stools in front of the conductor. Then with their usual brilliant agility they dived into a Handel concerto whose solo organ part had been transcribed for the quintet.

Dividing up the organ's multivoiced passages among the five instruments generated an exciting color and clarity which underlined the vitality of Handel's writing. After the Handel the ensemble indulged in a bit of its customary clowning with high-speed virtuosity in a piece of perpetual motion.

Conductor Jackson warmed up the orchestra a little more with Walton's "Crown Imperial," Coronation March, 1937, a satisfying earful of music. And then he proceeded at last to show his stuff with Britten's "The Young Person's Guide to the Orchestra" in an interpretation of exceptional finesse and polish. His ability to catch the pointed edge of a rhythm or the delicate curve of a melody revealed the score's many subtleties. Jackson's keen ear and refined touch also produced an exquisitely proportioned performance of Debussy's "Petite Suite," marred only by a rather abrupt handling of the ending.

Both the orchestra and the Canadian brass had good fun showing their more mellow side in the closing Duke Ellington medley.