INTERNATIONAL IMPROVISED MUSIC ARCHIVE - FREDERIC RZEWSKI (USA, b. 1938)
Frederic Rzewski is a composer, improvisor (co-founder of Musica Elettronica Viva) and pianist.
Compositions:
Spacecraft for large ensemble ad lib. (1967)
Sound Pool for large ensemble ad lib. (1969)
Second structure for solo or ensemble ad lib. (1972)
These are also available in German versions in Gronemeyer, Gisela and Oehlschlägel, Reinhard (ed) (2007): Frederic Rzewski: Nonsequiturs. Writings & Lecures on Improvisation, Composition, and Interpretation. / Frederic Rzewski: Unlogische Folgerungen. Schriften und Vorträge zu Improvisation, Komposition und Interpretation. Köln: Edition MusikTexte, Edition MusikTexte 009. - Some more works with flexible instrumentation may be found here - for instance Coming together! and Crusoe.