Henri Léon Marie-Thérèse Pousseur (23 June 1929 – 6 March 2009) was a Belgian classical composer, teacher, and music theorist.
Pousseur was born in Malmedy and studied at the Academies of Music in Liège and in Brussels from 1947 to 1952, where he joined the group called Variations associated with Pierre Froidebise. It was in this group that he first became familiar with the music of Anton Webern and other 20th-century composers. During his period of military service in 1952–53 at Malines, he maintained close contact with André Souris. He encountered Pierre Boulez in 1951 at Royaumont, and this contact inspired his Trois chants sacrés, composed that same year. In 1953, he met Karlheinz Stockhausen, and in 1956 Luciano Berio. A less-well-known influence from his early years was the powerful impression of listening to the music of Anton Bruckner, and he maintained a lifelong interest in medieval and Renaissance music, as well as in extra-European music and their practices.
In 1954, Pousseur married Théa Schoonbrood, with whom he had four children: Isabelle (1957), Denis (1958), Marianne(1961), and Hélène (1965).
Beginning in 1960, he collaborated with Michel Butor on a number of projects, most notably the opera Votre Faust (1960–68).
Pousseur taught in Cologne, Basel, and in the United States at SUNY Buffalo, as well as in his native Belgium. From 1970 until his retirement in 1988, he taught at the University and Conservatory of Liège, where he also founded the Centre de recherches et de formation musicales de Wallonie, in 2010 renamed as Centre Henri Pousseur. He died in Brussels, aged 79, on the morning of 6 March 2009, of bronchial pneumonia.
Generally regarded as a member of the Darmstadt School in the 1950s, Pousseur's music employs serialism, as well as mobile and aleatory forms, often mediating between or among seemingly irreconcilable styles, such as those of Schubert and Webern (Votre Faust). From the 1960's, Pousseur sought to develop his own serial style (to allow 'tonal' harmonies), and this can be heard in his orchestral composition Couleurs croisées (1967), which is based on the protest song We shall overcome.
His electronic composition Scambi (Exchanges), realized at the Studio di Fonologia in Milan in 1957, is unusual in the tape-music medium because it is explicitly meant to be assembled in different ways before listening. When first created, several different versions were realized, two by Luciano Berio, one by Marc Wilkinson, and two by the composer himself. Since 2004, the Scambi Project, directed by John Dack at the Lansdown Centre for Electronic Arts at Middlesex University, has focused on this work and its multiple possibilities for realization.
In addition to his compositional and teaching activities, Pousseur published many articles and ten books on music, amongst which are Fragments Théorique I: sur la musique expérimentale (Brussels: Université Libre de Bruxelles, 1970), Schumann le Poète: 25 moments d'une lecture de Dichterliebe (Paris: Klincksieck, 1993), and Musiques croisées (Paris: L'Harmattan, 1997). In 2004, two volumes of his collected writings, selected and edited by Pascal Decroupet, were issued by the Belgian publisher Pierre Mardaga Pousseau. He also published the first French translation of the writings of Alban Berg.