The Kronos Quartet celebrates its 40th birthday tonight with a reliably eclectic and stylish program. The foursome may be entering midlife, but there’s no sign of a crisis among the dozen pieces representing both the international and experimental axes of their charter. More traditional notes will be struck during world premieres by minimalists Terry Riley and Philip Glass, while Kronos’s global reach expands with works by Syrian pop star Omar Souleyman and Osvaldo Golijov’s five-quartet arrangement of El Sinaloense by Mexico’s Severiano Briseno. And the younger composers the group nurtures through commissions are represented by Bryce Dessner’s Aheym (Homeward), Aleksandra Brebalov’s Bubbles, and Jherek Bischoff’s A Semiperfect Number, whose title just about nails Kronos’s own charmingly imperfect mastery of the unknown.

Fri., March 28, 8 p.m., 2014