In its 23-year history Ensemble Intercontemporain has premiered almost 300 works, including more than 100 commissions, and its astonishing repertoire of over 1,400 20th-century chamber and orchestral pieces has earned it rock-star status in Europe’s classical music centers. Its popularity, unprecedented for a new-music group, has been matched by the adulation of critics and by generous subsidies from the French government; based at the state-run Cite de la Musique on the outskirts of Paris, the ensemble is regarded as something of a national treasure. Its president, composer and conductor Pierre Boulez, has never served as the group’s regular director, but he’s unquestionably its artistic conscience and guiding force. Not only did he persuade the French cultural ministry to fund the ensemble back in 1976–part of a vision that also included the government-sponsored Institut de Recherche et de Coordination Acoustique Musique (IRCAM), his incubator for electroacoustic experiments–but he recruited its top-notch instrumentalists, searching out players passionate enough to commit two-thirds of their time to the group. These days the 31 members collaborate closely with IRCAM composers and technologists, and usually get first dibs on the latest compositions by Boulez and his disciples. Perhaps by design, the ensemble’s strengths are best suited to the delicate and ethereal late-century French sound pioneered by its founder: it plays with precision and intellectual rigor, lucidly renders intricate rhythmic structures, and pays meticulous attention to minute shifts in sonority and texture. At this concert Boulez will lead the ensemble in his own Sur Incises (1998), elaboration on his 1994 solo piano piece Incises scored for three pianists, three harpists,’ and three percussionists. Also on the program are Schoenberg’s Suite, op. 29, and Linea, for two pianos, vibraphone, and marimba, by Luciano Berio, one of Boulez’s comrades in the postwar avant-garde. Monday, 8 PM, Orchestra Hall, Symphony Center, 220 S. Michigan, 312-294-3000 or 800-223-7114.