Information on differentia
A-Gu 29 and A-Gu 30 use tonary letters in the margins to indicate the differentiae. A tonary accompanies the two manuscripts on ff. 377v-379r of A-Gu 29. The images reproduced here are from this tonary. A few differentiae are notated on the staff in addition to, or instead of, the tonary letters, perhaps indicating changes to the choice of differentiae at a later date. The original indexing system in Cantus transcribed the tonary letters from the manuscript.
Downey, Charles, and Keith Glaeske. Inventory of Graz, Universitätsbibliothek, 30 (olim 38/9 f.). Edited by Debra Lacoste. In Cantus: A Database for Latin Ecclesiastical Chant. Directed by Debra Lacoste (2011-), Terence Bailey (1997-2010), and Ruth Steiner (1987-1996). Web developer, Jan Kolácek (2011-).