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Stockhausen set an ambitious goal: to erase the boundary between speech and synthetic sound. He broke down the voice of a 12-year-old boy into phonemes and analyzed their spectrum, then synthesized similar sounds using sine wave generators. In the piece, the live voice smoothly mutates into an electronic signal and back.

This was also the first work written for spatial reproduction: the music was broadcast through 5 groups of loudspeakers surrounding the audience. The sound literally flew around the hall, which in 1956 required complex manual coordination by sound engineers during the concert, as multi-channel tape recorders did not yet exist.