I set up the projection for our 9am “semitraditional” service, where we occasionally do a psalm with a sung congregational response (traditionally called an “antiphon”), and the verses chanted by choir and/or cantor. In such instances, I’ve found it useful to display the words of the verses in a slightly smaller font (about 20% smaller). Occasionally I’ll display the rubric “CANTOR” or “CHOIR” above the text to remove all doubt, but even just having the text appear in a different visual format hints to people that it is meant to be used in a different way, i.e. reading along in one’s head, rather than singing along.