A-Gu 29 and A-Gu 30 use tonary letters in the margins to indicate 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, 29 (olim 38/8f.). Edited by Debra Lacoste. In: Cantus: A Database for Latin Ecclesiastical Chant: Inventories of Chant Sources. Directed by Debra Lacoste (2011-), Terence Bailey (1997-2010), and Ruth Steiner (1987-1996). Web developer, Jan Kolácek (2011-).
Standardized manuscript tonary completed by Rebecca Shaw (Dalhousie University) on March 11, 2018. Edited by Jennifer Bain, Sister Ilaria Culshaw, Andrea Klassen, and Brayden Olson and (Dalhousie University) on August 8, 2019 and Rebecca Shaw on August 11, 2019.