The text-based notation system is pretty easy to master. The hard part is getting the rendering software set up and all the pieces playing well together. One of the forum members here set up an online processor so that you can run smaller jobs there instead of figuring it out yourself:
tomjaw's link, above, to a previous thread references an in-browser (Chrome plugin) tool based on Gregorio, which (if I remember correctly) has rendering capability, plus a link to a chant database. It's pretty cool.
For syllabic chant, such as the chants for the epistle or gospel for the Extraordinary Form of the Roman Rite, Gregorio is the way to. Using a Gregorian notation font such as Caeciliae in Adobe InDesign requires manual positioning of the text underlay which is a pain when there is a lot of text. Once you have one Gregorio file that produces the correct format, it will be easy to set up additional chants in the same format.
I would ask someone to provide a file for a Gloria or Credo in roughly the format you want for your output. Make sure you can get it to work in the online processor. Then change the titles, notation and text to what you need.
Changing the notation is straight-forward: enter the notes as letters in one section (a, b, c, ... g). Enter the text broken into syllables in the next section. Since the file is just a text file that you can edit with Notepad or Word, you can cut and paste your text from another source, then edit in the syllable breaks.
To participate in the discussions on Catholic church music, sign in or register as a forum member, The forum is a project of the Church Music Association of America.