What is "mixtur"

Mixtur, for orchestra, 4 sine-wave generators, and 4 ring modulators, is an orchestral composition by the German composer Karlheinz Stockhausen, written in 1964, and is Nr. 16 in his catalogue of works. It exists in three versions: the original version for full orchestra, a reduced scoring made in 1967 (Nr. 16½), and a re-notated version of the reduced scoring, made in 2003 and titled Mixtur 2003, Nr. 16⅔.