| Voice | Mass | Piece | Location | Folio | Staff/note | Error | Correction |
| D | 4 | Sequence, v. 10 | m. 13 n. 2 | c1v | st. 3 n. 3-4 end | note missing | inserted |
| D | 5 | Tract, v. 4 | m. 9 n. 2 | c4r | st. 5 n. 5 | minim | stem crossed out1 |
| D | 6 | Alleluia, verse | m. 16 n. 1 | d2v | st. 1 n. 8 | a' | lowered |
| D | 6 | Alleluia, verse | m. 21 n. 1 | d2v | st. 1 n. 15 end | c" | lowered |
| D | 6 | Sequence, v. 20 | m. 23 n. 3 | d3v | st. 4 beg. | g3 clef | lowered |
| D | 9 | Sequence, v. 2 | m. 13 n. 1 | f2v | st. 2 n. 19 | e" | lowered |
| D | 14 | Introit, verse | beginning | i1v | mensuration | 𝄵 | dot added inside the sign |
| D | 16 | Sequence, v. 6 | m. 3 n. 3 | k2v | st. 2 n. 6 | b' | lowered |
| D | 19 | Communion | throughout | m2v | st. 1-4 | g2 clef | raised2 |
| D | 20 | Alleluia, verse | m. 39 n. 1 | m3v | st. 3 n. 2 | g' | raised |
| D | 21 | Communion | throughout | n3r-n3v. | st. 5 ff. | flat signature | crossed out or erased |
| D | 24 | Sequence, v. 16 | m. 12 n. 2 | p2r | st. 4 n. 10 end | f' | raised |
| D | 25 | Introit | m. 8 n. 3 | p3r | st. 3 n. 4 | b-flat | raised |
| D | 25 | Alleluia, verse | m. 30 n. 1 | p3v | st. 5 beg. | g3 clef | lowered |
| A | 5 | Tract, v. 2 | m. 8 n. 1 | dd1r | st. 1 beg. | c4 clef | lowered |
| A | 5 | Tract, v. 4 | m. 31 n. 5 | dd1v | st. 1 beg. | c2 clef | raised |
| A | 10 | Introit | m. 29 | gg2v | st. 5 n. last | g | lowered |
| A | 10 | Sequence, v. 8 | m. 5 n. 1 | gg4r | st. 2 n. last | g | lowered |
| A | 10 | Sequence, v. 10 | m. 17 n. 3 | gg4r | st. 5 n. 10 | semiminim | marked to make white |
| A | 12 | Sequence, v. 8 | m. 5 n. 1 | hh4r | st. 5 n. 13 | extra f (semibreve) | crossed out |
| A | 12 | Communion | m. 2 n. 2 | ii1r | st. 2 n. 2 | dotted semibreve | stem added |
| A | 14 | Sequence, v. 20 | m. 3 n. 1 | kk2v | st. 2 beg. | c2 clef | raised |
| A | 14 | Sequence, v. 20 | m. 13 n. 3 | kk2v | st. 3 beg. | c2 clef | raised |
| A | 17 | Introit | m. 23 n. 1 | ll4r | st. 5 n. 12 end | e' | lowered |
| A | 18 | Introit | m. 2 r. 1 | mm2v | st. 1 after n. 14 | rest missing | added |
| A | 19 | Alleluia, verse | m. 37 | nn1v | st. 4 n. 8 | g' | raised |
| A | 19 | Alleluia, verse | m. 43 | nn1v | st. 4 n. last | d' | raised |
| A | 19 | Sequence, v. 12 | m. 21 after n. 4 | nn2v | st. 5 n. 11 end | extra g' (semiminim) | crossed out |
| A | 22 | Sequence, v. 18 | m. 17 n. 3-m. 18 | pp3r | st. 3 n. 1-3 end | g' f' f' (minim semibreve long) | g' f' e' d' d' (dotted minim semiminim minim semibreve long)3 |
| T | 6 | Sequence, v. 16 | m. 9 n. 2 | D3v | st. 4 n. 15 | c' | raised |
| T | 8 | Introit, verse | m. 12 n. 1-2 | E3v | st. 1 n. 2-3 end | e' c' | raised |
| T | 11 | Alleluia, verse | m. 50 n. 3 | G2r | st. 4 n. 3 | a | lowered |
| T | 11 | Sequence, verse 2 | signature | G2v | st. 1 beg. | flat too high | lowered |
| T | 11 | Communion | m. 9 n. 1 | G3r | st. 4 n. 1 | minim | stem crossed out |
| T | 12 | Alleluia | m. 4 n. 2 | G3v | st. 5 n. 13 | c' | lowered |
| T | 13 | Alleluia | m. 8 n. 3 | H1v | st. 5 n. 2 end | minim | stem crossed out |
| T | 14 | Sequence, v. 20 | m. 2 n. 2 | I1v | st. 4 n. 11 end | d' | lowered |
| T | 14 | Communion | signature | I2v | st. 1 | flat missing | added |
| T | 17 | Sequence, v. 4 | m. 11 n. 1 | K3v | st. 4 n. 1 end | semibreve | crossed out4 |
| B | 1 | Introit | m. 11 n. 2 | AA2r | st. 2 beg. | c5 clef | lowered |
| B | 4 | Tract, v. 4 | m. 5 n. 1-2 | CC2v | st. 5 n. 13-14 end | g a | lowered |
| B | 6 | Introit | m. 64 n. 1 | DD1r | st. 4 n. 4 | g | lowered |
| B | 6 | Introit | m. 66 n. 1 | DD1r | st. 4 n. 8 | g | lowered |
| B | 6 | Sequence, v. 14 | m. 6 n. 1 | DD3r | st. 4 n. 6 | f | lowered |
| B | 6 | Sequence, v. 18 | m. 15 n. 2 | DD3v | st. 2 n. 11 | c' | lowered |
| B | 7 | Introit | m. 1 n. 1 | DD4r | st. 5 n. 1 | minim | stem crossed out or erased |
| B | 8 | Introit, verse | m. 20 n. 1 | DD4v | st. 1 n. 5 end | d | lowered |
| B | 8 | Sequence, v. 18 | m. 7 n. 1 | EE4r | st. 4 beg. | flat too high | lowered |
| B | 8 | Sequence, v. 18 | m. 15 n. 2-3 | EE4r | st. 5 n. 10-11 end | notes missing | inserted |
| B | 8 | Communion | m. 19 n. 1 | FF1r | st. 1 n. 15 end | g | lowered |
| B | 9 | Introit | m. 24 n. 1 | FF1v | st. 1 n. 1 | black semibreve | marked to make white |
| B | 9 | Alleluia, verse | m. 63 | FF2r | st. 2 n. last | B-flat | raised |
| B | 13 | Sequence, v. 22 | mm. 4-5 | HH4r | st. 3 n. 11-12 | semibreve semibreve | ligature stem crossed out or erased |
| B | 13 | Communion | m. 38 n. 1 | HH4v | st. 3 n. 4 end | d | lowered |
| B | 15 | Introit | m. 31 n. 1 | II3r | st. 5 n. 12 | e | raised |
| B | 16 | Sequence, v. 12 | m. 3 n. 1 | KK2v | st. 3 n. 3-4 | note missing | inserted |
| B | 18 | Introit | m. 48 n. 3 | LL1v | st. 4 n. 6 | e | raised |
| B | 18 | Introit | m. 49 r. 1 | LL1v | st. 4 after n. 6 | rest missing | inserted |
1. The correction is incorrect. Smudges in some copies may be attempts to undo it.
2. Correction in errata sheet at end of vol. III (T).
3. Correction in errata sheet at end of vol. III (T). Also added by hand in some copies.
4. The correction may be incorrect. The editors have omitted the note, but it should perhaps be restored.