Copy of Mozart's Fugue in C minor, KV426
Without any doubt, Mozart's Fugue in C minor for two pianos, KV426, is one of the greatest fugues ever written since the death of J.S.Bach. A staggering amount of canonic devices is let loose on the fugue's main subject, while maintaining a remarkable clarity of texture, demonstrating Mozart's total control of counterpoint. At the same time the music is pervaded with a holy anger one expects of a Beethoven, rather than a Mozart. In short, Mozart combines in this unique masterpiece Bach's intellectual techniques with Beethoven's deep passion. It's therefore important to realize that Beethoven not only knew Mozart's fugue, but even made a copy of it in his own handwriting. We must assume he was impressed by this work. It's somewhat surprising that, as far as we know, Beethoven never attempted to compose a similar fugue himself.
This copy was mistakenly identified by Hess as an arrangement for string quartet by Beethoven, and was therefore given a number: Hess 37. The pages of the copy got scattered all over the world; presently the pages 1-2 and 5-6 are in the Robert Owen Lehman Collection in the Pierpont Morgan Library, New York, while the pages 3-4 are in the Beethoven-Haus, Bonn.
There are 36 minor deviations in the copy compared to Mozart's original, most of them mere slips of the pen. Yet there are also several improvements by Beethoven, cf. the following revision account for the details.
Revision account. Page 1. 1. bar 7, Left Hand 2nd piano, 1st and 2nd beat: the natural is missing before the E flat in Beethoven's copy. 2. bar 11, LH 2nd piano, 1st beat: natural missing before the A flat. 3. bar 14, LH 1st piano, 2nd beat: natural missing before the B flat - Beethoven thinks this to be in G minor, against Mozart C minor? 4. bar 17, Right Hand 1st piano, 3rd and 4th beats: trill missing on A flat. 5. bar 19, RH 1st piano, 2nd beat: Beethoven seems to have two 16th E flats, against Mozart a single 8th E flat. 6. bar 20, RH 2nd piano, 1st beat: Beethoven writes a G, against Mozart an E flat. This is not a slip of the pen; in so doing Beethoven corrects the concealed octave between RH 2nd piano and LH 1st piano. Page 2. 7. bar 24, RH 1st piano, 2nd beat: flat before D is missing. 8. bar 25, RH 1st piano, 3rd beat: apparently Beethoven misses Mozart's point here: chromatic anticipations are the key feature of this motif, only here the chromatic anticipation occurs before a F sharp, that's to say: an E sharp. Therefore Mozart writes a double augmentation before the E flat: a natural followed by a sharp. Beethoven gives the natural to the E flat, but the sharp to the following, 2nd, F sharp, where it is strictly speaking superfluous. 9. bar 32, RH 2nd piano, 3rd and 4th beats: trill missing on E flat. 10. bar 37, RH 1st piano, 2nd beat: natural missing before the B flat. Page 3. 11. bar 46, RH 1st piano, 4th beat: flat missing before G. 12. bar 50, LH 1st piano, 4th beat: Beethoven puts a natural before the A flat (although there is an A flat in the 2nd piano on the same beat). Does he interpret this as being in B flat minor, while Mozart clearly intends D flat major? 13. bar 52, RH 2nd piano, 1st beat: Beethoven has a G, against Mozart an E flat. 14. bar 52, RH 2nd piano, 3rd and 4th beats: trill missing on C. 15. bar 59, LH 2nd piano, 4th beat: natural missing before A flat. Page 4. 16. bar 63, RH 1st piano, 4th beat: Beethoven writes A flat - B, against Mozart: A - B; even more remarkable because an 8th earlier, on the same beat, Beethoven writes, following Mozart, A - B in the RH of the 2nd piano. 17. bar 69, LH 1st piano, 3rd beat: flat before B missing. 18. bar 76, LH 2nd piano, 3rd and 4th beats: Beethoven has added a flat to the trill on C; this is an improvement since the bar is in F minor. Page 5. 19. bar 81, LH 1st piano, 2nd beat: trill missing on C. 20. bar 81, RH 2nd piano, 3rd and 4th beat: natural missing before G. 21. bar 81, LH 2nd piano, 4th beat: trill missing on B. 22. bar 85, LH 1st piano, flag of the last 8th note missing. 23. bar 86, RH 2nd piano, 4th beat: tie to the 1st beat of bar 87 missing. 24. bar 88, RH 1st piano, 4th beat: Beethoven has here a quarter note, instead of an 8th rest followed by an 8th note. 25. bar 88, LH 1st piano, 4th beat: E should be E flat. 26. bar 89, RH 1st piano, 3rd beat: C instead of E flat. 27. bar 89, RH 2nd piano, 4th beat: F instead of A flat. 28. bar 90, RH 1st piano, 1st beat: D instead of F. When seen in context, it becomes clear that deviations 26, 27 and 28 are no slips of the pen on Beethoven's part, but deliberate changes to Mozart's text. By increasing the intervals from a third to a fifth in all these three cases, Beethoven wants to highten the expressiveness of the melodic lines. 29. bar 98, RH 2nd piano, 3rd beat: Beethoven deliberately changes Mozart's B flat to a B natural. Page 6. 30. bar 105, LH 2nd piano, beats 3 and 4: naturals before the A flats are missing. 31. bar 108, LH 1st piano, beat 4: natural before F missing. 32. bar 108, LH 2nd piano, beat 4: natural before F missing. 33. bar 112, LH 2nd piano, 1st beat: F should be G. 34. bar 113, RH 2nd piano, 4th beat: natural before B flat missing. 35. bar 114, LH 2nd piano, 1st beat: F should be G. 36. In the final 4 bars the 2 pianos play in unison, and rather than writing out the 2nd piano part in full, Beethoven merely indicates it should follow the first piano. In so doing, he overlooks the fact that in bar 118, LH 2nd piano, 4th beat, the G drops one octave compared to the first piano.