Stimmung, for six vocalists and six microphones, is a piece by Karlheinz Stockhausen, written in 1968 and commissioned by the City of Cologne for the Collegium Vocale Köln. Its average length is seventy-four minutes, and it bears the work number 24 in the composer's catalog. It is a tonal, and yet also a serial composition. It is "the first major Western composition to be based entirely on the production of vocal harmonics", the first "to use overtones as a primary element". An additional innovation is "the unique kind of rhythmic polyphony which arises from the gradual transformation/assimilation of rhythmic models". Title The German word Stimmung has several meanings, including "tuning" and "mood". The word is the noun formed from the verb stimmen, which means "to harmonize, to be correct", and related to Stimme (voice). The primary sense of the title "implies not only the outward tuning of voices or instruments, but also the inward tuning of one's soul". According to the composer, the word Overview Stimmung is in just intonation. Six singers amplified by six microphones tune to a low B1 drone, inaudible to the audience, and expand upwards through overtone singing, with that low B's harmonics 2, 3, 4, 5, 7, and 9 (B2, F2, B3, D4, A4, and C5) becoming in turn fundamentals for overtone singing. It is composed using what the composer calls moment form, and consists of 51 sections (called "moments"). The harmonies of Stimmung are composed from 108 pitches: twelve different tones for each of the three women's voices, and twenty-four for each of the three men. Not only do the performers produce partials from the overtone series in each note they sing, but all of the fundamental tones are also related by whole-number overtone ratios. In this way, overtones are composed upon overtones, generating a range of degrees of harmonic fusion. According to the 1986 Hyperion Singcircle liner notes: The order of the rhythmic models and the distribution of the poems and "magic names" are decided by the performers, but the sequence of pitches in the 51 moments is fixed. Though the 1968 "Paris version" used by the Collegium Vocale Köln at the world première has been published (as No. 24½ in Stockhausen's catalog), the 1977 "Singcircle version" (directed by Gregory Rose) has been well documented in , and both versions have been performed throughout the world. Singcircle performances include the Round House on