Unsichtbare Chöre
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Unsichtbare Chöre (Invisible Choirs) is an eight-channel electronic-music composition by Karlheinz Stockhausen. A component part of the opera Donnerstag aus Licht, it may also be performed as an independent composition, in which form it is designated "ex 49" in the composer's catalog of works (where Nr. 49 is Michaels Jugend, act 1 of the opera).