Expo is the penultimate in a series of works dating from the late 1960s which Stockhausen designated as "process" compositions. These works in effect separate the "form" from the "content" by presenting the performers with a series of transformation signs which are to be applied to material that may vary considerably from one performance to the next. In Expo and three companion works (Kurzwellen for six performers, Spiral for a soloist, and Pole for two), this material is to be drawn spontaneously during the performance from short-wave radio broadcasts (Kohl 1981, 192–93). The processes, indicated primarily by plus, minus, and equal signs, constitute the composition and, despite the unpredictability of the materials, these processes can be heard from one performance to another as being "the same" (Kohl 2010, 137).
Each plus, minus, or equal sign indicates that, upon repetition of an event, the performer is to increase, decrease, or maintain the same level in one of four musical dimensions (or "parameters"): overall duration of the event, number of internal subdivisions, dynamic level, or pitch register/range. It is up to the performer to decide which of these dimensions is to be affected, except that vertically stacked signs must be applied to different parameters (Stockhausen 1973, 1, 11, 21). Despite this indeterminacy, a large number of plus signs (for example) will result in successive events becoming longer, more finely subdivided, louder, and either higher or wider in range; a large number of minus signs will produce the reverse effect (Kohl 2010, 137). To the signs previously used in Prozession, Kurzwellen, and Spiral Stockhausen adds some new ones.
In 1968 the West German World Fair Committee invited Stockhausen to collaborate on the German Pavilion at the 1970 World Fair in Osaka, Japan. Other collaborators on the project included the pavilion's architect, Fritz Bornemann, Fritz Winckel, director of the Electronic Music Studio at the Technical University of Berlin, and engineer Max Mengeringhausen. The pavilion theme was "gardens of music", in keeping with which Bornemann intended "planting" the exhibition halls beneath a broad lawn, with a connected auditorium "sprouting" above ground. Initially, Bornemann conceived this auditorium in the form of an amphitheatre, with a central orchestra podium and surrounding audience space. In the summer of 1968, Stockhausen met with Bornemann and persuaded him to change this conception to a spherical space with the audience in the center, surrounded by loudspeaker groups in seven rings at different "latitudes" around the interior walls of the sphere (Kurtz 1992, 166; Föllmer 1996). In addition, Stockhausen would participate by presenting daily five-hour programs of his music (Kurtz 1992, 178). Stockhausen's works were performed for 5½ hours every day over a period of 183 days to a total audience of about a million listeners (Wörner 1973, 256). Expo was written, as the title indicates, for these performances and was composed in Kürten in December 1969 and January 1970, at that time under the working title of Trio (Stockhausen 1978, 152). Between 14 March and 14 September 1970, Expo was played and sung many times at the German Pavilion at Expo '70, in daily performances by twenty different musicians including the composer (Stockhausen 2009, 260). The English group Intermodulation (Roger Smalley, Tim Souster, Peter Britton, and Robin Thompson) performed it a number of times and made recordings for the radio (Stockhausen 1978, 152). It is one of the few Stockhausen works that have not been released on a commercial recording.
Structure and technique
Expo is a more relaxed and cheerful piece than its companions, and features an unusual degree of synchronised gestures and canonic imitation (Maconie 2005, 324). It consists of a sequence of approximately 135 events, grouped into two large sections divided in the score by wavy barlines, each interrupted once by an insert lasting up to 2½ minutes. One of these inserts is slow, the other fast; both are characterised by a synchronised periodic beat. Stockhausen explained that in pieces like this, "the first step is always that of imitating something and the next step is that of transforming what you're able to imitate" (Cott 1973, 33).
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- Frisius, Rudolf. 2008. Karlheinz Stockhausen II: Die Werke 1950–1977; Gespräch mit Karlheinz Stockhausen, "Es geht aufwärts". Mainz, London, Berlin, Madrid, New York, Paris, Prague, Tokyo, Toronto: Schott Musik International. ISBN 978-3-7957-0249-6.
- Fritsch, Johannes, and Richard Toop. 2008. "Versuch, eine Grenze zu überschreiten … Johannes Fritsch im Gespräch über die Aufführungspraxis von Werken Karlheinz Stockhausens". MusikTexte no. 116 (February): 31–40.
- Hopp, Winrich. 1998. Kurzwellen von Karlheinz Stockhausen: Konzeption und musikalische Poiesis. Kölner Schriften zur neuen Musik 6. With CD recording. Mainz and New York: Schott. ISBN 3-7957-1895-3.
- Kohl, Jerome. 2010. "A Child of the Radio Age". In Cut & Splice: Transmission, edited by Daniela Cascella and Lucia Farinati, 135–39. London: Sound and Music. ISBN 978-1-907378-03-4.
- Maconie, Robin. 2005. Other Planets: The Music of Karlheinz Stockhausen. Lanham, Maryland, Toronto, Oxford: The Scarecrow Press, Inc. ISBN 0-8108-5356-6.
- Stockhausen, Karlheinz. 1971. "Ein Abend EXPO 70". In his Texte zur Musik 3, edited by Dieter Schnebel, 229–31. DuMont Dokumente. Cologne: Verlag M. DuMont Schauberg. ISBN 3-7701-0493-5.
- Stockhausen, Karlheinz. 1973. Nr 27 Spiral für einen Solisten. (score) UE 14957. Vienna: Universal Edition.
- Stockhausen, Karlheinz. 1978. "Pole für 2 (1969–70) und Expo für 3 (1969–70)". In his Texte zur Musik 4, edited by Christoph von Blumröder, 152. DuMont Dokumente. Cologne: Verlag M. DuMont Schauberg. ISBN 3-7701-0493-5.
- Stockhausen, Karlheinz. 2009. Kompositorische Grundlagen Neuer Musik: Sechs Seminare für die Darmstädter Ferienkurse 1970, edited by Imke Misch. Kürten: Stockhausen-Stiftung für Musik. ISBN 978-3-00-027313-1.
- Wörner, Karl Heinz. 1973. Stockhausen: Life and Work, translated by Bill Hopkins. Berkeley: University of California Press.