The title already reflects a very special element of this work as there is always one ossia-instrument; either the violin (when the clarinet plays) or the clarinet (when the violin plays). It is possible to formalise this incident. The title then reads as follows: when A (the clarinet) plays, B (the violin) does not play. Hence the piece may be performed in two ways. The two instruments, however, do not make use of ordinary tones, but instrument- (or, respectively, instrument-group-)specific extended techniques. The respective other instrument translates these sounds. As the sounds are very specific, a seamless translation may, however, not always be achieved. Therefore, the clarinetist, for instance, utilises a table in order to imitate the hits on the body of the violin. The piece is divided into two parts, while an intermezzo (slightly rapid tempo) is placed between part A (moderate tempo) and part B (slow tempo). In terms of the structure, homophonic and polyphonic sound layers alternate between the instruments. The two form sections are also divided concerning their sound-wise qualities. The division starts with the intermezzo, while certain techniques (such as cluster and harmonics) are introduced here and encroach upon part B.