Rienäcker studied musicology from 1959 to 1964 (minor subject: "art science'") with Ernst Hermann Meyer, Georg Knepler, Walther Vetter, Peter H. Feist and Carl Heinz Claasen at the Humboldt University of Berlin, and also musical composition with Hans Georg Görner.
From 1964 to 1966 Rienäcker worked as music dramaturge (for opera, operetta, concert) at the Landestheater Eisenach [de].
There he obtained a doctorate in 1973 with a thesis on dramaturgical principles in operas by Paul Dessau, Siegfried Matthus, Udo Zimmermann and Robert Hanell.
In 1984 he habilited on the dramaturgy of the finale in operas by E. T. A. Hoffmann, Louis Spohr, Carl Maria von Weber and Heinrich Marschner.
[2] Among his academic students were Peter Wicke, Daniela Reinhold, Antje Kaiser, Susanne Binas-Preisendörfer, Sebastian Klotz and Aniara Amos [de].