I ring the bell when our priests receive from the chalice; (the bishop too, for that matter) this was taught to me by a traditional priest, and it is largely a European practice, but it is an ancient tradition. He was trained in Rome, and I trust his expertise in this matter. The Bell is to signify the moment that the sacrifice is actually complete. (Part of sacrifice is the consumption of the offering.) our bishop, who lived in Rome for many years, has also never said anything. And he would certainly correct me if he was not a fan, or if it was somehow in contravention of a rubric. He is an extremely intelligent man and is very precise when it comes to liturgical matters.

My straightforward reading of the GIRM is that you should start chanting immediately, however, in practice, I find it much more comfortable to allow 30 seconds of silence, and then begin chanting the moment the priest then begins to prepare for distribution for holy communion. There’s nothing wrong with 30 seconds of silence. In fact, waiting a few seconds or not starting until after the priest has finally completed the sacrifice also functions as a cue for everyone else that it’s time for the motion to begin. It also reinforces the solemnity of the moment that the priest receives because we’re not trying to cover it up.

It was formerly (another parish, another diocese) my practice to begin while the celebrant is receiving. A former pastor emphasized to me that this was good because it connected the communion of the priest and the communion of the faithful as a unified event. My current pastor has asked me to wait until he has received from the chalice, so that’s what I do now. This makes sense in my parish since we do both the old and the new rites and this makes the former more like the latter in terms of when the communion antiphon is sung, namely at the beginning of the distribution of Holy Communion.

Tbh it’s a post hoc justification which is fine, but…the bell is totally superfluous in any form of the rite. Either you commune or you don’t. Aren’t there enough signals to come forward if you are that don’t intrude on the chant and, frankly, the solemnity of the moment?

In the Novus Ordo, the instructions are explicitly to begin as the priest receives Communion, so that is what is appropriate. It's not ambiguous. There is no rationale in favor of delay; it's not as if the priest is going to be leading the singing.

GIRM 86. *While the Priest is receiving the Sacrament, the Communion Chant is begun,* its purpose being to express the spiritual union of the communicants by means of the unity of their voices, to show gladness of heart, and to bring out more clearly the “communitarian” character of the procession to receive the Eucharist. The singing is prolonged for as long as the Sacrament is being administered to the faithful. However, if there is to be a hymn after Communion, the Communion Chant should be ended in a timely manner.

(emphasis added)

GIRM 86 is very pastoral in its nature with its very modern liturgical sensibilities (gladness, community). Since happily in the last 50 years we have discovered that Modern Man is the same creature as Pre-Vatican II Man and still craves silent adoration and abhors tedious musical repetition, GIRM 86’s directions to avoid silence and sing a single communion chant ad nauseam are happily ignored in my experience.

This is one of the problems with making it a rubric one way or the other: too early, deprive schola of communion; I believe in allowing people to commune as they wish (within reason; I don’t like it at weddings and at Requiem Masses or on certain large occasions). Too late, no psalms to extend the proper. All Saints and Beati Mundo Corde are a good example of a proper that is too long to repeat if you sing the proper at the ablutions (pre-1957).

On Rogation Monday and a few other days the schola goes first and then immediately sings the proper. It’s a bit awkward. But we need to do it.

When we begin the music varies a bit.

When a choir is singing in the loft, we at least get the instrumental music started promptly, and then bring in the singers once the pianist or organist has decided they have given enough of an introduction (one tends to improvise very long introductions, which are quite nice, so I don’t object). Generally the choir takes a brief moment to receive communion, extraordinary ministers come up to the loft and it takes about the length of hymn for them to get there. Then a second hymn or song tends to be about the amount of music needed to cover communion and at least part of the purification of the vessels.

When we have a small ensemble off by the side altar niche (that no longer has an altar, thank you 1970s) they will approach the altar with extraordinary ministers to receive communion and then begin the music.

Personally I do like an antiphonal style communion chant or song, something that has a part that can easily be sung in procession, and than can be varied in length as needed, and then ended promptly when the procession ends. Following that up with either silence or light organ music, and letting people kneel or sit pray privately for a while…, and then singing a Eucharistic hymn of thanksgiving really works rather nicely where it is done thing (and hymn singing means standing back up again), once the congregation gets used to it. Then use an organ recessional after the dismissal instead of a “sending” hymn (or silence in Lent, etc.).

There is an idea in many places that the communion song should not begin until the procession of the congregation, and I can’t figure out quite where that idea comes from. Often some sort of instrumental filler may be used from the priest’s communion up until then, especially where a good bit of time to organize the extraordinary ministers is needed.