230r
Folio 230r (Figure 1) contains a curious musical addition that has not yet been identified. This folio relates part of the mass for the Finding of the Cross (May 3). The beginning of the alleluia verse "Dulce lignum dulces" has been covered by a slip of parchment bearing a textless melody that is notated on a four-line staff with an F clef. Figure 2 shows the original melody, a setting of the word "Alleluya," underneath. (Click on the image to the left once to view its metadata, and again on that page to view a high-quality version.)
What to make of the addition? It seems unlikely that it is related to "Dulce lignum dulces": the alleluia verse is in mode 8, while the added melody is squarely in mode 1 or 2 (note the 5-step descent from A to D on the pasteover in Figure 1). It is also possible, though unlikely, that it was intended as a cadence for the communion chant for the Feast of Philip and Jacob, "Tanto tempore," which lies on the first half of the leaf.
Summary
Although the musical additions in Western MS 97 lead us no closer to the manuscript's chronological or geographical origins, they remind us that the medieval liturgy was a living and continuously negotiated tradition. As the manuscript changed hands over the years, later scribes corrected and altered the chant repertory according to the standards of their chapters.