Laura, in addition to the 18 Masses in the Gradual (or Liber Usualis), you should find a section of 'ad libitum' settings of the various parts of the ordinary. This section includes a few more settings of the Sanctus and Agnus Dei.
As far as other settings, my understanding that there are a vast number of these in the manuscript tradition. Whether or not they have been published, or are available on line, I don't know, but I'd bet someone on this forum knows. When Solesmes compiled our modern Gradual and Liber, they made a selection, which is where where we got the 18 settings plus the ad libitum.
I hope someone chimes in with info about where to find these. It's something I'd like to know about too.
Thanks for the responses! This is very helpful!
To make sure that I understand, please correct me if I'm wrong: Solesmes publishes pretty much all of the chant (for the Ordinary, and for the Priest's parts, and for the people's responses (such as "Dominus vobiscum" "Ite, Missa Est" etc., for the Latin Rite) that IS published. There probably is a lot of other chant out there, but it's still in the manuscripts, and nobody has copied/edited/published it yet. If I have their resources, and have carefully looked them over, there's not much more to find?
Jahaza:
"and the only way to really preserve music is to keep singing it."
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