Once attributed to Johann Ludwig Krebs, the "Fuge über das Magnificat" BWV 733 is now definitely acknowledge as stemming from Johann Sebastian Bach himself. It is a fugue in four parts, ending in five parts.The fifth voice gloriously reintroduces the subject as the augmented "cantus firmus" in the bass. Such a fugue shows much of a flamboyant "fantasia". According to Peter Williams, "Here, the writing is closer to the big organ fugues - compare its close with BWV 540 or 545 - and the two five part sections are as well conceived as anything in mature Bach." ( In "The Organ Music of J. S. Bach", p. 476, 2nd edition -2003- Cambridge University Press).
This masterpiece was passed down to us thanks to copies by or via (Op. cit., p. 474) Oley, Kirnberger and Krebs (two copies).
Musical score: "BACH - Organ Works - Bärenreiter - Urtext der Neuen Bach-Ausgabe. Herausgegeben von HANS KLOTZ" - Band 3