As always, I note the kind contribution of Richard Chonak who translated the Latin original of the second edition (1988). Today, we look at the situation when there are two readings, not three, in the Liturgy of the Word:
9. When there is only one reading before the Gospel, the Gradual Responsory is sung after it, or the Alleluia with its verse. In Paschaltide, either one of the Alleluia chants is sung.
10. At the singing of the Gospel, after the final proper cadence, the conclusion Verbum Domini is added, as notated in the common tones; then all respond: Laus tibi, Christe.
For a weekday Mass, sing the Psalm or the Alleluia. During Easter, sing either Alleluia chant.
11. The Credo is sung in the customary manner either by all or in alternation.
12. The Universal Prayer [Prayer of the Faithful] is carried out according to local custom.
I’ll state the singing of the Credo has always been a mystery to me. For the faithful to state the faith: this seems a spiritual priority, and if a musical setting can enhance it, well and good. But if the musical setting were in any way an obstacle, the sung version should be dropped.
Catholic Sensibility 
I suppose it all depends on what purpose you see for the Profession of Faith at the Eucharist. If it is a restatement of doctrine, they it makes sense to recite, but if it is a joyful expression of our faith, they we should always be singing it. I like to think of the Creed as the same as the Gloria in the Eucharist, something we join our voices together to celebrate. I think we need to sing the Creed a lot more. Overall, I think we need to sing a lot more.
“A joyful expression of faith.” Hmm, I can get my head and heart around that.