Lost&Found editions are not critical editions as those on the Archive of Iberian Polyphony. They are, however, entirely reliable for the purposes of analysis and performance insofar as unmarked editorial interventions, like emendations, are kept to a minimum. Badly damaged sources (for instance, portions of P-Cug MM 3 and, particularly, P-Cug MM 44) were treated digitally so that readings were always unambiguous. Pieces that required a large amount of conjectural reconstruction (like the Kyrie of Missa Tu es Petrus, the Benedictus and Agnus Dei of Missa sine nomine, and the setting of Psalm Memento Domine) were not included in the sample for producing analytical observations.
Prefatory staves. These appear in the PDF editions for each piece. Prefatory staves show the original opening clefs, stave signatures (if any), and mensural signs present in the source. Prefatory staves do not appear in the MEI files.
Voice-names. These follow the source, and so they may vary from one piece to the next. If voices are not named in the source, suitable names in square brackets are provided by the editor.
Note-values. Original note-values are retained throughout. Final notes, regardless of their original form, take the shape of a longa, even if its value exceeds the last bar in the piece, section, or movement of a piece.
Bar-lines. Bar-lines are regularly placed on the staves according to the original mensural sign. Occasional instances of irregular barring may occur without further notice.
Clefs and pitch. Original clefs are replaced by modern clefs according to the range of each voice-part. Music is not transposed even when notated in high clefs, always keeping the original written pitch.
Triple and sesquialtera proportions. These are denoted by figure 3 in the MEI files and rendered in 3/1 or 3/2 metre in the PDF editions.
Ligatures and coloration. Ligatures are indicated by a horizontal square bracket over the notes concerned. Coloration is indicated by a broken horizontal square bracket over the note, or notes, concerned. These indications do not appear in the MEI files.
Accidentals. Accidentals placed before a note are present in the source. These accidentals apply until the bar-line unless cancelled. Editorial, implied, and cautionary accidentals are placed above the notes concerned. Editorial accidentals apply to the note concerned and any immediate repetition of the same note. Original redundant accidentals are always retained.
Chant. Sections in chant present in the source are reproduced in the original square black notation with the clef modernised. Sections in chant only appear in the PDF editions.
Lacunae. Missing portions of music and other notational elements editorially reconstructed are placed in square brackets. These brackets are not shown in the MEI files.
Text. Texts given in italics represent the realisation of textual repeat signs in the source. Texts provided in square brackets are editorial. As most copyists took little or no care with regard to the alignment of syllables and notes, detailed distribution of the text is mostly editorial. Spelling, syllable division, capitalisation, and punctuation have been adapted according to the standards of sung ecclesiastical Latin as in the Liber usualis, however the /ei/ diphthong in "eleison" was kept, as is common in Portuguese sources.