During the holidays West Point military academy has a "holiday celebration", where their choir sung many traditionally secular holiday songs, sleigh bells, marshmallow world etc. However they also song Rudolph the red nose reindeer and at least one song I believe had some non-secular lyrics, but the lyrics the snippet I saw didn't include anything Christian (I think joy to the world? I don't recall now). They were singing in a church.
West Point is a military academy under the Department of Defense, so presumably it's still bound by separation of church and state. Thus any choir the spent money funding I would think needs to be careful about not explicitly celebrating Christmas. I'm curious what leeway they have to fund a choir that has 'Christmas' songs in their list, before they open themselves up to complaints of violating church and state. For that matter if they had done more Christmas music, really blatant celebration of Christmas instead of the holidays, and someone went out of their way to cause trouble over the lack of separation would there be any actual legal recourse, or would it not be an actual violation of the rules about separation of church and state?
Most of their songs were clearly chosen to be secular holiday songs, so does the number of songs matter, can they get away with a few christian only ones? Rudolph the red nose reindeer was obviously a reference to Christmas, but a mostly secular aspect of Christmas tradition, is the lack of religious importance to Rudolph relevant in being able to address it etc?