Here you can find transcriptions of the Chants (mostly from Graduale Triplex) with St. Gallen neumatic notation.
For every PDF file there is a GABC file too, with NABC notation included.
The PDF files are produced using GREGORIO software - https://gregorio-project.github.io/
The TEX file used for compiling is main.tex
- copy the file (i.e. in-myintroitus.gabc) to this directory
- run following command: make file=in-myintroitus.gabc