Mention "new music" and "string quartet" in a sentence, and "Kronos Quartet" will surely follow. Contemporary music is the group's eminent domain; its performers have taken over not as usurpers, but as brave new world virtuosos who stand apart with a repertoire made up largely of works written exclusively for them. The Kronos Quartet's pan-ethnic program at the Hirshhorn Museum Saturday evening included composers from five continents, exposing cultural diversity, warts and all. Every piece was performed with commitment and deep sensitivity. Yet it seemed odd that traditional Kronos encore jazz numbers (arrangements of Thelonious Monk and Bill Evans) were given priority over newer, and frankly better, compositions. A recent arrangement of John Coltrane's "Naima" didn't translate well; a madcap, twisted tango inserted in the first half would have been much more effective as an encore. As it turned out, two selections from the quartet's latest record -- "White Man Sleeps No. 1" by South African Kevin Volans and "Morango, Almost a Tango" by Thomas Oboe Lee -- concluded.

Barto'k's String Quartet No. 4 made a strong impact from a historical standpoint. Considering that the work is 60 years old (making Barto'k the graybeard in Kronos' canon), it sounded every bit as fresh as its predecessors on the bill, particularly Roberto Sierra's "Memorias Tropicales," which builds on Barto'k's advanced pizzicato and glissando techniques.