Church instructions are clear that the Mass is not to be delayed by music.
The Entrance
47. After the people have gathered, the Entrance chant begins as the priest enters with the deacon and ministers. The purpose of this chant is to open the celebration, foster the unity of those who have been gathered, introduce their thoughts to the mystery of the liturgical season or festivity, and accompany the procession of the priest and ministers.
. . .
Greeting of the Altar and of the People Gathered Together
49. When they reach the sanctuary, the priest, the deacon, and the ministers reverence the altar with a profound bow. As an expression of veneration, moreover, the priest and deacon then kiss the altar itself; as the occasion suggests, the priest also incenses the cross and the altar.
50. When the Entrance chant is concluded, the priest stands at the chair and, together with the whole gathering, makes the Sign of the Cross. . . .
I emphasize "When the Entrance chant is concluded" because it seems to me that only after it ends can the priest stand for the sign of the cross.
A close reading of this section suggests to me that when the presider senses that the celebration has been opened, the unity of those gathered has been fostered, the thoughts of all have been introduced to the mystery of the season or festivity, then he signals to the schola that it is time to sing the doxology and thus to bring the entrance chant to an end.
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