It is a German-language edition: title pages and notes by editors are exclusively in German.
A supplemental volume was published in 1926, a quarter of a century after the Bach Gesellschaft's dissolution.
Another late addition to the series was Max Schneider's 1935 revision of the fourth volume.
All volumes, including the 20th-century additions, were published by Breitkopf & Härtel.
[1][2][3] Gustav Mahler owned 59 of the 61 volumes of the Bach-Gesamtausgabe, and used them for his arrangements of some of Bach's compositions.