Barry Tuckwell makes playing the French horn seem as simple as picking out a tune on a penny flute.

Appearing last night at Wolf Trap with that National Symphony, he walked out on stage, took position with his right hand in the bell of the instrument, and glided right into a mellifluous performance of Strauss first horn concerto.

His graceful agility and the beautiful even tone never faltrered despite the sultriness of the weather, which left many of the coatless orchestra members and conductor Leonard Slatkin mopping their faces.

Slatkin, who takes over the St. Louis Symphony this fall, combines exceptional clarity of direction with a passionate approach to music. He knows how to get a variety of colors from the orchestra and how to use those colors for expressive ends. He is particularly adept at achieving a wide and flexible dynamic range. His finely shaded direction of Vaughan Williams' "Fantasia on a Theme by Thomas Tallis" brought to mind appropriately for this most English of composers, the shadowed interiors of old English cathedrals.

Though he brought considerable intensity and intelligence to Bartok's "Cocerto for Orchestra," Slatkin does not yet seem to have this brilliant, moving work quite in hand. But he is certainly headed in the right direction and with time should find the added weight and sharper edge which the music demands.