 The treatment of space as a musical parameter is one of the most important preoccupations of Xenakis' music, particularly in his works of the mid-to-late 1960s.The dramatic impact of utilizing the performance space in this manner is evident in many passages throughout the piece in which accents or imitative rhythms are passed around the ensemble.The percussionists use a wide range of instruments and sound effects during the piece, including sirens, maracas, and pebbles, along with an arsenal of drums, wood blocks (simantras), cymbals, and gongs.