Musik im Bauch (Music in the Belly) is a piece of scenic music for six percussionists and music boxes composed by in 1975, and is Number 41 in his catalog of works. The world premiere was presented on 28 March 1975 as part of the Royan Festival. The performance was given by Les Percussions de Strasbourg in the haras (horse stable) in the town of Saintes, near to Royan. Its duration is roughly 38 minutes.
Stockhausen dreamed Musik im Bauch in 1974, seven years after coining the phrase during a memorable evening with his daughter Julika, when she was two years old. All of a sudden, she had all sorts of noises in her insides, and he joked with her, "You have music in your belly!" The phrase prompted the toddler to erupt in laughter, throwing her arms in the air and endlessly repeating "Music in the belly!" Her laughing fit lasted so long that Stockhausen became concerned about her. She only gradually stopped laughing after he put her in bed, where she kept repeating the phrase and giggling as she fell asleep (, 248). The first sketch is a single leaf dated 28 February 1974, with brief and fragmentary written notes about the general musical and theatrical course. In the published score, Stockhausen claims it is an exactly written version of what he dreamed (, XIV). However, some important details from the first sketch were later discarded. The first three melodies later used in this piece, "Aquarius", "Leo", and "Capricorn", were composed in preliminary form later in 1974 during one or more of Stockhausen's composition seminars at the Hochschule für Musik Köln. These melodies were later modified (Conen 1991, 195).
In order to present the piece, Stockhausen composed twelve melodies for the zodiac signs, which can be performed independently as . He found a Swiss manufacturer of musical boxes, Reuge, and he hired them to make the boxes, believing that there were no previous original compositions for music boxes in existence (, XX).
In Stockhausen's composition catalog, Musik im Bauch is the 41st entry. It spawned at least ten subentries, including Tierkreis, which is numbered as 41½. Musik im Bauch has been characterized as "a fairy tale for children" (Maconie 1976, 322), "a vision of ritualistic savagery" (Schiffer 1975, 49), "a blend of fairy tale with American Indian tribal myth" (Maconie 2005, 370), or else as "a ritual played out in Mexican Indian scenery" (Kurtz 1992, 205).