What Do We Sing?
Good news! There is an official, prescribed "What" to sing for the Holy Sacrifice of the Mass! It's been very clearly and consistently laid down throughout Church history, and though the wording of council documents is often vague, Vatican II didn't change that. Once more for the people in the back:
(except to allow the use of the vernacular language with the local bishop's permission)
The implications of this are huge. There seems to be a general understanding that what the Vatican II documents said is far less important than what a handful of people want the documents to mean, and that's why the state of Liturgy In The Church Today is kind of a mess. I have sat through liturgies containing Beatles songs, Bob Dylan, an Agnus Dei that started with the exact same intro as a Pearl Jam song, Jazz Masses, and more. "As long as it helps me pray" is the watchword of the day, even though such a phrase is even more nebulous than the council documents themselves.
Music for the liturgy can't be based on individual taste, because the liturgy is universal; at the Holy Sacrifice of the Mass, those of us on Earth are taken outside of time and united with Christ on the Cross, together with the saints and angels in Heaven. We don't create the liturgy, we enter the liturgy. We can't force our own moods and personalities out of time and into eternity with us, demanding that the saints and angels join us in singing number 436 in the red hymnal, Star-Child, number 436*. God brings His mood and personality, so to speak, to us, and we receive.
Well, what are the Propers for the day? They are scriptural texts (with a few exceptions) similar to the Responsorial Psalm, and they already have tunes. You can find them in the lectionary, in various books on the internet, and more and more often, you can find hymnals and missals that print them. Of course, to sing them in their Gregorian form would involve Latin (which, once again, Vatican II still says should be the default language), so if your parish is just beginning to move in a more traditional direction, this is probably not where you are going to start.
Where are you going to start? Most parishes in Canada and the US today use a musical structure known derisively by some as the Four Hymn Sandwich. Setting aside for the moment the condescension of those who typically employ it, the sense is this: there are four "slots" to fill with a hymn, you plug in four hymns and you're good to go. This is actually a really good starting point for someone about to take a bite out of liturgy planning, but a starting point is all it is. And if you don't pay any attention to what you are plugging in, your sandwich isn't going to have anything to do with the actual Sacred Feast going on at the altar - and it's going to be a sad substitute, too.
I'm going to go more in depth into each "slot" in the liturgy in the near future, (EDIT: I did!) so I'll wrap this post up with a practical tip: get your hands on a source for the text of the Propers. I'll list a few below. When it's time to choose your music for the liturgy, pray to the Holy Spirit, then read them first. Ever since I began using the Propers instead of the readings (which I also read) as a basis for choosing music, our hymns and our homilies have been in ever-greater harmony with each other. Hooray for the Holy Spirit!
Simple English Propers by Adam Bartlett - linked above. Gregorian melodies from the Latin are adapted to fit the English language, rather than trying to squish English words over the exact same square notes, which somehow always ends up having the most decorative melismata on the word "and" or something
Vatican II Hymnal - I don't recommend it as a hymnal, but is has all of the readings (including Propers) for the whole liturgical cycle in the back. I use it only for planning.
*This is a real entry in a real red hymnal. We use this book in our parish. It literally refers to Jesus as a Love Child.