 .are made audible by an active process of sound detection (comparable to the auscultation of a body by a physician); the microphone is used actively as a musical instrument, in contrast to its former passive function of reproducing sounds as faithfully as possible” .Together with Stockhausen's immediately preceding work "Mixtur", for five orchestra groups, four sine-wave generators, four ring modulators, they form a tryptych of live-electronic works, where electronic transformations are accomplished during the performance (as opposed to studio-produced electronic music on tape).