Mozart’s unfinished Mass in C minor, K. 427 (‘Great Mass’) History, Theory, and Practice of its Completion

Like his famous Requiem, Mozart’s Mass in C minor, K. 427, remained incomplete. The instrumentation of two Credo movements composed in outlines, was left unfinished. The rest of the Credo and an Agnus Dei are missing altogether. The Sanctus and Benedictus were completed but their main scores have gone lost and have to be reconstructed from Mozart’s surviving wind score and secondary sources.A historical completion of the Mass, like Süssmayr’s of Mozart’s Requiem, does not exist. Available editions date from 1901 to 2016. Against all of these serious criticism can be raised. The hypothesis defended in this dissertation is that it is possible to arrive at a much more convincing completion by combining the most recent findings of historical musicology, skill and expertise in historically informed music theory (analysis, counterpoint, harmony, arranging, including a thorough knowledge of Mozart’s individual style), and experience with historically informed performance practice.Part A of the thesis summarizes the current state of historical research about the work, discusses the autograph and secondary sources in detail, analyses the work in relation to Mozart’s completed works and other composers’ works known to have inspired him (Bach, Handel), explores the possibilities for completion, discusses the versions published so far, and offers a new completion. Part B is a full score of the newly completed movements ‘Credo in unum Deum’, ‘Et incarnatus est’, Sanctus, and Benedictus, part of the new edition of the Mass (© 2017 by Breitkopf & Härtel, Wiesbaden). Editorial additions are printed in grey.