“Sing to the Lord” now online
http://www.usccb.org/liturgy/SingToTheLord.pdf
I haven’t read it yet - will update with thoughts when I have.
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UPDATE 1:
76. “The assembly of the faithful should participate in singing the Proper of the Mass as much as possible, especially through simple responses and other suitable settings.” When the congregation does not sing an antiphon or hymn, proper chants from the Graduale Romanum might be sung by a choir that is able to render these challenging pieces well. As an easier alternative, chants of the Graduale Simplex are recommended. Whenever a choir sings in Latin, it is helpful to provide the congregation with a vernacular translation so that they are able to “unite themselves interiorly” to what the choir sings.”
I think a lot of people may read this in a way to which many of us will object. It seems to give priority to congregational hymns; however, if you look at the wording, there really is no poo-poo’ing of choral singing of, say, a Gregorian introit. It simply says that when the congregation doesn’t sing, chants from the RG are appropriate. (That doesn’t mean that they are inappropriate when the congregation DOES sing...)
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UPDATE 2:
“157. The proper or seasonal Responsorial Psalm from the Lectionary for Mass, with the congregation singing the response, is to be preferred to the gradual from the Graduale Romanum.”
“162. The Gregorian settings of the Gospel Acclamation are most appropriate for use in those communities which are able to sing the response communally.”
This I don’t particularly like. ISTM there are legitimate reasons for using the graduals and Gregorian alleluias/tracts.