"This was [for] a documentary program about the Tuareg tribe. The Tuareg tribe are nomads in the Sahara desert and I think they live by bartering, taking salt, I think it was, across the desert. In the piece [...] I tried to convey the distance of the horizon and the heat haze and then there's this very high, slow reedy sound. That indicates the strand of camels seen at a distance, wandering across the desert. That in fact was made from square waves on the valve oscillators we've just talked about, but square waves put though every filter I could possibly find to take out all the bass frequencies and so one just hears the very high frequencies. It had to be something out of this world. "