Very uncommon AMQS from important French composer and conductor, one of the major innovators and forces in 20th century music. 20.5 x 27.5 cm page inscribed beneath a mounted halftone photograph with three detailed measures of music with text, the opening measures of his 1957 work "Improvisation sur Mallarmé" for Soprano and 7 Instruments, beginning "le vierge, le vivace, et le bel aujourd'hui," signed "avec cordial sympathie / P. Boulez." Mounted to another sheet, else fine.