In this light another general tendency of composers after World War II is not at all surprising: their demand for new sound materials. The ordinary orchestra, even as expanded by Debussy, Stravinsky, and others, now struck them as stiff and antiquated. They explored new sonorities — noises, unexpected new sounds squeezed out of old instruments, and an infinite range of musical materials produced not by instruments at all, but by electronics.

It began with composers making new demands on the standard sources of music. Singers were instructed to lace their singing with hisses, grunts, clicks, and other “nonmusical” noises. Pianists had to stand up, lean over the piano, and pluck the strings or hit them with mallets. Using a special kind of breath pressure, clarinetists learned to play chords called multiphonics — weird-sounding chords by conventional standards but fascinating to those attuned to the new sound universe.

Western orchestras and chamber music groups had always been weak in percussion, as compared to their counterparts in many non-Western cultures and to jazz. But in the postwar era marimbas, xylophones, gongs, bells, and cymbals of many kinds — percussion instruments that had been used only occasionally in the classical music of earlier times — became standard.

However, the truly exciting prospect for new sonorities in music emerged out of technology developed during the war: the production of music by electronic means.