The Publication in facsimile of the auto graphic copy of Johann Sebastian Bach’s Mass in A major BWV 234 at the occasion of the Bach Anniversary Year 1985 has been made possible thanks to the generous support of the publishing house which so carefully preserved this precious manuscript in its archives for almost 200 years. The manuscript was acquired long ago by Johann Gottlob Immanuel Breitkopf, the brilliant and dynamic forefather of the publishing house Breitkopf & Härtel, who conducted a prosperous business selling music transcriptions in Leipzig. It is still unclear as to how he obtained the manuscript. Perhaps it had belonged to the estate of Wilhelm Friedemann Bach, from whom Breitkopf apparently acquired a part of his Bach collection. The earliest reference to the manuscript’s change of ownership is found in Breitkopfs Verzeichniß Musicalischer Werke of 1761, which includes Bach’s Missa, a 2 Flauti, 2 Violini, Viola 4 Voci, Organo under the listing of copies of unpublished compositions. The copy was available at the price of 2 thl. (thalers) 12gl. (groschen). A few years later, in 1769, the same offer appeared again together with other works by Bach or ascribed to him in the Verzeichniß lateinischer und italiänischer Kirchen-Musiken of Bernhard Christoph Breitkopf & Sohn. In more recent times, the work has been mentioned in Wilhelm Hitzig’s Katalog des Archivs von Breitkopf & Härtel, revised in 1925, together with the continuo part, which was included with the copy and which was also originally written in Bach’s own hand. The economic reorganization of the publishing house Breitkopf & Härtel after the Second World War made it necessary to sell the manuscript together with other works from the publisher’s archives. This manuscript was to have been put up at auction by the auction house J. A. Stargardt. The catalogue, containing an informative commentary by Wolfgang Schmieder, was already printed, but before the auction could take place, the land of Hesse decided to purchase all the manuscripts, thus preventing the dispersion of this valuable collection. The manuscript was officially handed over to the Hessische Landes- und Hochschulbibliothek in Darmstadt on 29 October 1953. The A major Mass is still preserved there today, together with its fellow piece, the Mass in G major BWV 236.