In the mid-1970s, sound artist Max Neuhaus came up with a creative use of NPR's Round Robin phone loop. Using this system (which allowed different affiliate stations to broadcast programs airing in other towns), he connected the phone-in banks of five stations, encouraged listeners to call in and whistle, and then looped these five cities of whistlers through a phase-shifter.
The result was a 2-hr long broadcast of a creepy, meandering, experimental soundscape that could have easily been mistaken as a takeover of earth's communications systems by alien overlords.
Listen to a sample snippet of the broadcast [MP3]
via Music Thing