One group of folios near the end of the manuscript is misbound. The correct order is as follows: 236, 238, 237, 240, 239, 241. In the index, these folios have been renumbered in order to restore the correct order of chants; sorting on the numbers in the "Marginalia" field will restore the misbound order of the folios in the manuscript. The ordering of these folios is also corrected in the facsimile reproduction of the Penpont Antiphoner. There is a detailed codicological analysis of the manuscript in the introduction to that work.
The numbering of the differentiae in this index follows that of the Sarum Tonale (published by Frere in The Use of Sarum ). In it, as here, the tonus peregrinus is assigned to mode 8 differentia 5. Six of the differentiae in the "Penpont" antiphoner are indicated by pitches or neumations that are slightly different from those in the Sarum Tonale: these are 1.8, 2.2, 3.2, 3.3, 3.5, and 4.2. In addition, two differentiae (4.9 and 7.7) that appear in the Sarum Tonale are lacking in the "Penpont" antiphoner. One differentia in "Penpont," 2.3, appears to be a variant of either 2.1 or 2.2, but it is impossible to determine which. This differentia is not in the Sarum Tonale.
- Edwards, Owain Tudor. Matins, Lauds, and Vespers for St. David's Day. Cambridge: D. S. Brewer, 1990.
- Frere, Walter Howard, ed. The Use of Sarum, II. The Ordinal and Tonale. Cambridge: Cambridge University Press, 1901.
- National Library of Wales MS. 20541 E: The Penpont Antiphonal. With an Introduction by Owain Tudor Edwards. Publications of Mediaeval Musical Manuscripts, No. 22 (Facsimile Reproduction of the Manuscript). Ottawa: The Institute of Mediaeval Music, 1997.