Damien,

In the Sanctus you use the leap of a minor 7th. As a rule, congregations which need to be included by the use of refrains won't attempt a 7th without scooping -- see "Go tell it on the mountain" or "On Eagle's Wings", where the 7th is a major 7th.

CGZ- I beg to differ with your "rule" assignation, and particularly with the supporting examples. For example, the major seventh you imply in OEW is part of the verse, which most informed, competent musicians would assign to a capable soloist. The other interval receiving more attention is the leap from low A-F# via E (5-2-3), easily negotiated by congregations. Regarding the spiritual/carol, I don't program it often, but the minor seventh never gives congregations fits. Your characterization precludes musical context being a factor. In "Toolanbread" sister has the full octave ascending leap which also doesn't confound the average pew singer, likely because of its springboard setup. Intervals, especially ascending, aren't as difficult to navigate as are the over-nuanced sixteenth note ornaments mentioned elsewhere, or even the persistent triplets found in tunes like EBENEZAR, or awful ones like the unusable hemiolas in "Somos el Cuerpo." . YMMV

Melo, you assume church musicians are informed and competent.