lecture on Stockhausen's use and interpretation of shortwave broadcasting
You can hear it, but you cannot see or touch it. It isn't surprising that wireless transmission from its very beginnings triggered the metaphysical imagination of certain people, one of the most famous ones being Thomas Edison. Radio could allow us to receive messages from beyond the grave or from outer space, we just need to know where to listen for them, between the stations...
To this day people are researching and recording what are called "Electronic Voice Phenomena" or EVP. So we wouldn't be too far off to see Stockhausen's use of shortwave radio as "Electronic Music Phenomena". Where John Cage used radio as just another instrument, allowing for randomized surprises, Stockhausen, during what probably was the most metaphysical phase in his career in the sixties would rely on shortwave radio as a source of musical information, asking his musicians to translate that information into music. He used shortwave radio in quite a few pieces, the main one being the apt titled "Kurzwellen". "Kurzwellen" was one of the works performed during the legendary concert in the Lebanese Caves of Jeita in November 1969. This event was documented by the French television (ORTF) and its producer Luc Ferrari.