The Eastman School of Music, through it's mother institution, the University of Rochester, is digitizing hundreds of public domain music scores, and making them available for free online. I wanted to link to a couple which may be of interest to Catholic Church musicians.
Choix de musique religieuse comprenant 191 motets a 1, 2 et 3 voix avec accompagnement d'orgue dans le style Cécilien ... par Emile Dethier.
https://urresearch.rochester.edu/institutionalPublicationPublicView.action?institutionalItemId=14407&versionNumber=1
(a collection of Latin motets for 1, 2, or 3 voices collected by a Belgian organist and church musician)
60 motets avec accompt. d’orgue ou piano pour messes, saluts, mariages, offices divers - Charles Gounod
https://urresearch.rochester.edu/institutionalPublicationPublicView.action?institutionalItemId=5060
(only the first 20 motets, for solo voice or 2 voice duets)
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