I don't know why I've never noticed this before:
At the Chabanel Psalms site, on the Accompaniments page (with NOH), there is a Polish Kyriale Accompaniment book. It includes the three most common Messes du Plainchant by DuMont, beginning on pg. 91 on the book (98 of the PDF scan).
Here is the direct link: http://sci.pam.szczecin.pl/~splawgo/Missae.pdf. It can also be accessed via the Chabanel Psalms.
At the Chabanel Psalms site, on the Accompaniments page (with NOH), there is a Polish Kyriale Accompaniment book. It includes the three most common Messes du Plainchant by DuMont, beginning on pg. 91 on the book (98 of the PDF scan).
Here is the direct link: http://sci.pam.szczecin.pl/~splawgo/Missae.pdf. It can also be accessed via the Chabanel Psalms.