I did employ a strict organization of the material and the form, which is related to serial composition, but neither the compositional technique nor the realization of an abstract notion was the most important thing for me. Primary were ideas of widely ramified musical labyrinths.
György Ligeti, 1960

The orchestral work Apparitions, which premiered in 1960 at the International Society for Contemporary Music festival in Cologne, brought Ligeti his international breakthrough. Atmosphères, presented a year later, requires a huge orchestral apparatus: the motivic material in the more than 80 instrumental parts is rich in variation and sounds simultaneously with small temporal shifts. The result is a "dense fabric" in which the individual threads can no longer be distinguished. Ligeti thus created a sound whose "state of aggregation" changes extremely slowly and kaleidoscope-like. He called this technique "micropolyphony". Characteristic features of Apparitions and Atmosphères are internal tension and unexpected turns that evoke anxiety. Musical labyrinths result from the simultaneity of stasis and inner movement.