IN a maroon turtleneck and loose-fitting gray suit, eyes on his score, Pierre Boulez took turns one late August morning here rehearsing the soloists for “Répons.” Written in 1981 for six soloists, chamber orchestra and live electronics, it is the first major work he wrote using the electronic-music institute in Paris, Ircam. But it has rarely been performed, just a few dozen times.
Now Mr. Boulez had young musicians from the Lucerne Festival Academy on hand. Intimations of jazz, Balinese gamelan, African drumming and Japanese music floated from welters of rapid passagework. “You are freer there, so to speak,” he reminded the harpist where the score mandated improvisation.
“No, no, no, no,” he gently chided one of the pianists, adding, consolingly, “It’s difficult also for the conductor, believe me.”
It sounded nearly impossible, not least when the six soloists finally played together before the rehearsal broke. Intense complexity created waves of impenetrable sound.