23. The Alleluia or, as the liturgical season requires, the verse before the Gospel is also a “rite or act standing by itself.”  It serves as the greeting of welcome of the assembled faithful to the Lord who is about to speak to them and as an expression of their faith through song.
The Alleluia or the verse before the Gospel must be sung, and during it all stand. It is not to be sung only by the cantor who intones it or by the choir, but by the whole of the people together. 
The Gospel Acclamation is not just walking music, or a filler piece in between the second reading and the Gospel. It is a stand-alone rite. For clergy and musicians, the challenge is how to demonstrate that. My suggestion is a high-quality repertoire, plus the investing of rehearsal time. For composers, a setting would be essential to any work purporting to be a “Mass setting.”
“(A)n expression of faith through song” implies this is a credal statement. What faith are we expressing? Wouldn’t it be the presence of Christ in the proclamation of the Gospel.?
This is one of those rare occasions when the Church requires singing. Furthermore, the body of worshipers are to sing it, not just choir, not just the songleader. Does this abrogate the usual practice of having the people sing the Alleluia and the cantor or choir the Gospel verse? I wouldn’t think so. What do you think about it? About any of this?