Information on differentia
Differentiae are indicated throughout the manuscript by tonary letters in the margins that refer to a tonary that provides the adiastematic neumes for each of the tonary letters. The tonary is split between 390 and CH-SGs 391, with some pages missing. Reconstructed in their original order, the tonary is as follows: pp. 1-2, 195-202 (1-8 of CH-SGs 391), 457-458 (263-264 of CH-SGs 391), 3-4, 193-194, 187-188, 455-456 (261-262 of CH-SGs 391), 5-6. An outline of the distribution of the tonary between the two volumes is handwritten on the inside fly-leaf of CH-SGs 390. The twelfth-century tonary from 388 was used to fill in any missing tonary letters in the 390 and 391 tonary. For the rationale of the transcription of adiastematic neumed differentiae into pitched notation, see Rebecca Shaw's thesis. The differentiae in this tonary are also transcribed into pitched notation in P. Ephrem Omlin's Die Sankt-Gallischen Tonarbuchstaben(Regensburg: Friedrich Pustet, 1934).
Helsen, Kate. Inventory of Sankt Gallen, Stiftsbibliothek, 391. Edited by Andrew Mitchell and Debra Lacoste. In: Cantus Manuscript 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-). Omlin, P. Ephrem. Die Sankt-Gallischen Tonarbuchstaben. Regensburg: Friedrich Pustet, 1934.
Images: St. Gallen, Stiftsbibliothek, Cod. Sang. 390, pp. 1-6, 187-188, 193-194 ; Cod. Sang. 391, pp. 1-8, 261-264