The performers in Kurzwellen react to the completely unforeseeable events which they receive on short-wave radios while performing on their instruments. But this is not improvisation. Stockhausen’s score instructs them how to transform what they hear: how they imitate amd modulate it, make it longer or shorter, how to rhythmically articulate it, higher or lower, louder or softer, darker or more playful. Whether they should play and as solo, duo, trio or quartet, etc. Though not so familiar now, at the time short-wave radios made it possible to listen to live radio stations from all over the world. The transmission was not always clean, but disturbed by noises and interferences. Moving from one station to another one could hear Morse-code signals, amateur radio communications and all kind of electronic sounds and noises. Stockhausen wanted this sound world to be part of Kurzwellen. This new version created by C.L.S.I., premiered at the Stockhausen Summer Course in Kurten on August 10th 2011, is a kind of updating of Stockhausen’s one of the 1960s. It is the first version using computers and multiple live electronic performers. Instead of Stockhausen as sound projectionist doing all live electronics himself, in this version there are four pairs of musicians and electroacousticians.