The instrumentation was quite novel for Western music at the time, lacking any kind of bass instrument, and drew some influence from the sound of non-Western instruments. The xylorimba recalls the African balafon; the vibraphone, the Balinese gamelan; and the guitar, the Japanese koto, though "neither the style nor the actual use of these instruments has any connection with these different musical civilizations" ("Speaking, Playing, Singing" (1963) in ). Boulez chose the collection with a continuum of sonorities in mind: "a number of features shared by these instruments (forms) a continuous passage from voice to vibraphone" . The purpose is to allow a graduated deconstruction of the voice into percussive noises, a compositional technique which has been common throughout Boulez's work (e.g. the recent "Sur Incises" of 1998 similarly breaks down the sounds of the piano by combining it with harp and percussion). The voice and five pitched instruments can be arranged in a line, each pair connected by a similarity, as in the following diagram (quoted from ):