In 'Radio Net', the mixing was done with what could be seen as a special case of time-division multiplexing. Although heard as a conventional mix of input signals, the output was actually being switched very quickly from input to input. The perceived level of an input in the mix depended on how long the output lingered on it. The technique allowed automatic mixing according to an analysis of each signal; the criterion I used here was that the highest pitched signal at any given instant won the output for that particular fraction of a second. A week before the broadcast, I shipped these self-mixers to the engineers at the stations in each of the call-in cities and hooked up and debugged them over the phone. In those days radio programs on NPR were distributed by what they called a Round Robin - telephone lines connecting all two hundred stations into a large loop stretching across the country. Any station in the system could broadcast a program on all the others by opening the loop and feeding the program around it. I saw that it was possible to make the loop itself into a sound-transformation circuit and tried a few things with it in several preliminary studies in 1974 For the broadcast I decided to configure it into five loops, one for each call-in city, all entering and leaving the NPR studios In Washington. Instead of being open loops as usual during a broadcast, though, I wanted to close them and insert a frequency shifter in each so that the sounds would circulate; it created a sound-transformation 'box' that was literally fifteen hundred miles wide by three thousand miles long with five ins and five outs emerging in Washington We had a "dress rehearsal" the day before the broadcast so I could get a feel for things. It is touchy when you put a wire that long in a loop; even if you do have a frequency shifter and gain control, each loop was in a sense a living thing - they could get out of hand very quickly. During the broadcast I was on a conference call with the five engineers and could listen to each loop and ask them for changes in shift and gain at any time. My role was holding the balance of this big five-looped animal with as little movement as possible. In all the previous works I had left the nature of the sounds phoned in for each caller to decide. Here I wanted to provide an indication to try and move them past the "Listen, it's my voice on the radio" stage and towards listening to one another. The question was what kind of indication - how does one indicate something to perhaps half a million people with their diverse backgrounds, intentions, and ways of interpreting? I decided to ask them simply to whistle. The results of asking half a million people to do anything, even something as simple as whistling, of course will be diverse. Some will do it; others won't. Those who do will choose how or what to whistle. Even though it may seem a very specific request, for me it was a broad indicator to provide a body of pitched material in the work. During the broadcast, the sounds phoned into each city passed through its self-mixer and started looping. With each cross-country pass, each sound made another layer, overlapping itself at different pitches until it gradually died away. It was quite a beautiful Sunday afternoon - two hours over which ten thousand people found their way into the work and made sounds.