The Ames Quartet is not a string quartet but a piano quartet -- violin, viola, cello and piano, one of the most heavenly combinations of instruments around. Its members -- violinist Mahlon Darlington, violist Laurence Burkhalter, cellist George Work and pianist William David -- are completely attuned to one another, and also to the subtleties of the music they play.

Their concert yesterday evening at the National Gallery of Art was a mesmerizing, if somewhat one-sided, affair. It wasn't merely the fact that their program was contemporary in nature, but that the first two of the three works performed -- Copland's Piano Quartet and Gary White's "Epitaph" -- shared a slow, mournfully serene quality. This is not to say that the pieces are harmonically alike: The Copland unfolds in long lines and sets forth a spare tonal palette that calls to mind open fields and endless skies, while White's piece (in its Washington premiere) is a lusher, and eventually more urgent, work.

For its last selection, the Ames left these somber realms for the much more unconventional terrain explored by William Bolcom in his 1976 Piano Quartet. The first movement begins with the strings gradually ascending, sounding very much like a blender working its way up to pure'e. Things get stranger still: the third movement has the piano lapsing into a sleepy New Orleans piano bar blues, and the close is as harmonically straight and sweet as can be. For an encore, the Ames repeated the piano bar blues; one could almost see curls of smoke wafting over the players' heads.