Resources for chant propers
There is an excellent resource for choirs wishing to sing the propers of the Mass. St Isaac Jogues Chant Resources has the score and an mp3 file for the Introit, Offertory and Communion, and the Gradual and Alleluia according to the Chants Abrégés. this is still a work in progress and not all the files are there yet, but there is plenty to be getting on with. There are resources for both the ordinary and extraordinary form.