A German composer and conductor. Also co-publisher of magazins on musical theory.
He studied musical theory at Mainz, Zurich and Berlin, and composition with G. M. Koenig in Utrecht, The Netherlands. In 1969 he formed, together with Heinz-Klaus Metzger the Ensemble Musica Negativa, with strong ties to Theodor Adorno's Negativen Dialektik, and commitment to the performance of works by John Cage, Hans-Joachim Hespos, Dieter Schnebel, Morton Feldman, Earle Brown and Christian Wolff.
From 1977 to 2003 Metzger and Riehn published the Musik-Konzepte in the Munich edition text + kritik; in 1984 they received the Deutschen Kritikerpreis. They continue their main work in the series querstand. musikalische konzepte. They also edited the two volumes of compositions by Adorno.
In 1987 Riehn and Metzger worked as chief dramaturgs at the Frankfurter Oper under Gary Bertini, where they initiated the composition and performance of Cage's Europeras 1 and 2.
He died in 2015