I find that singing down to B♭2 in "Silent Night" at church is pretty hard. I think the key of C or C♯ is better for me. How do people with high voices deal with this? Do they just keep silent or what do they do?
I'll leave this one to the ineffable Douglas Adams
That part of a hymn (usually a few notes at the end of a verse) where the tune goes so high or low that you suddenly have to change octaves to accommodate it.”
The range is an octave and a fourth - a bit more than a lot of commonly sung songs, but not too bad for most singers, depending, of course, where it starts.
Most people will jump an octave (up or down) when something is getting out of their range, but given that a sort of average range is round two octaves, I think, there's scope for this being in several different keys, all of which are singable to the general public.The more usual situation is, I believe, is that the high notes are more problematic than the low ones.
When I ran choirs, I'd start Silent Night in A, go to Bb, and end in C, and there was never any problem.