This article describes the theories and practices of the German installation artists and composers Sabine Schäfer and Joachim Krebs. Much of their work concerns site-specific sound installations involving the articulation of time and space. Their principal work methods and materials are described. In addition, they have formulated a typology of five installation types which they describe using their own installations as examples. Each installation type responds to a particular set of aesthetic and practical challenges both for the artists and the visitors. These are discussed and illustrated in the article. The typology extends beyond the specific work of these artists and can be applied to installations in general, thus providing a framework for critical analysis. Furthermore, the translators have discussed the issues regarding the specialised vocabulary of the artists and the rendering of such language into English. (Ralf Nuhn, John Dack, article translation and afterword.)