Alexander Klar Alison Knowles art movement Ben Patterson Ben Vautier body Dick Higgins Emmett Williams experimental Geoffrey Hendricks George Brecht George Maciunas Germany happenings heritage history iconoclasm impact interdisciplinary intermedia internationalism Joe Jones Joseph Beuys live art methods Milan Knizak motifs Nam June Paik participation Philipp Corner playfulness Robert Fillou Sarah Maske score spectators Stefan Fricke Takako Saito transience transient uniqueness Wiesbade Wolf Vostell