Richard Ales has the happy ability to endow everthing he conducts with a touch of drama. He needed every bit of this talent last night during the program of American music for strings that his National Gallery Orchestra played in the East Garden Court, for, along with a few gems, there were several pieces of an unusually dreary nature.

On the pleasant side were the opening Quintet by the 18th-century John Frederick Peter, a chip straight off the Viennese school block, a cheery and well put together Theme and Variations by Genevieve Fritter, a member of the violin secton, and Bales' own arrangement of Some Stephen Foster Quadrilles.

The rest of the program was turgid; a Lamentation by Clark and one of Hovhaness' innumerable modal settings of a Psalm and Fugue, both ponderous and self-important, and, after intermission, John Vincent's Symphony No. 2 for Piano and Strings. Its three movements charge about busily, always seeming to be about to say or do something important, but never quite getting to it. After the echoes die away, there is emptiness rather than substance.

Elizabeth Stevens was an extremely incisive and effective soloist here, and, with Bales' collaboration, made the best of a dubious thing.