François-Xavier Roth has been closely associated with the Boulez Ensemble ever since the opening of the Pierre Boulez Saal in March 2017. The first of their two joint programs this season is dedicated entirely to the music of Boulez. In addition to the early, groundbreaking Sonatina for Flute and Piano and Messagesquisse, a 1976 birthday greeting for Paul Sacher, another of the composer’s fascinating scores will be heard for the first time in “his” hall: the unfinished double work Éclat/Multiples, written between 1966 and 1970.