Stumbled across this online resource and found it a valuable cross-reference of chant themes to Tournemire pieces. It includes the actual chant scores from the Paroissien Romain (i.e., the Graduale).
For a fuller understanding of the chants used in LOM, please consult Robert Lord's 1983 article which notates all of the chants. It is also found in the CMAA book, Mystic and Modern, editted by Jennifer Donelson and Stephen Schloesser.
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