Karlheinz Stockhausen's Tierkreis is a cycle of 12 melodies inspired by the star signs of the Zodiac and the planets and deities traditionally associated with that ancient system, as well as what the composer referred to as the "Twelve Human Characters". Conceived and scored for any combination of improvisers and/or a set of specially constructed music boxes, it has been interpreted by a more numerous and varied range of artists than virtually any other work in the Stockhausen oeuvre. In July 2002, trombonist Michael Svoboda and five similarly intuitive musicians collaborated on a realization of more than 75 minutes in duration, which was released on the Wergo label the following year. This recording features cellist Scott Roller, bass clarinetist Michael Riessler, accordionist Stefan Hussong, double bassist Wolfgang Fernow, and drummer/vibraphonist Michael Kiedaisch. While Svoboda's construct "keeps to the sequence of the astrological year," it consists of two interwoven versions with the movements grouped in threes (according to seasons) and played twice to create a sort of double helix. For the first realization, the players "approached the composition the way jazz musicians approach a standard," internalizing and then reproducing it "quasi-improvisationally." The second version employed freer improvisation over a pre-recorded stratum and introduced the original music boxes. The balance between freedom and structure is beautifully maintained so that the two become essentially synonymous. Tierkreis grew from Musik im Bauch and provided the seeds for the chamber opera Sirius. Stockhausen's final work was an orchestral setting of Tierkreis, completed on December 4, 2007. He passed away on the following day.
The first original composition ever devised for music boxes, Tierkreis was conceived and created in the same period as Musik im Bauch (Music in the Belly), a theater ritual during which ambulatory percussionists cut open the belly of an eagle-headed anthropomorphic sculpture and pulled out music boxes. During the fall and winter of 1974-1975, Stockhausen visited the Jean Reuge music box factory in St. Croix, Switzerland, studying how the little mechanisms operated and researching possible modifications, including the installation of multiple teeth for the same tone. Three zodiacal airs were used for Musik im Bauch (Leo, Capricorn, and Aquarius). Nine more were written during the spring and summer of 1975 to complete the cycle of Tierkreis. Each melody employs all of the notes in the chromatic scale, is entirely free of motivic elaboration, and appears to have transcended the patterns of traditional serial and 12-tone methodology. Portions of Tierkreis were used to form the central Wheel Section of the vocal/instrumental/electronic chamber work Sirius, which has been described as a visual representation of the annual cycle. In a moving posthumous tribute, the carillon within the bell tower of the city of Cologne has been programmed since 2009 to play one of the airs from Tierkreis each day at 12 noon.