Oh God, now I'm having visions of a bunch of seasoned Waulkers singing He Mandu* and the guitar guy feeling the need to strum along. Choral singing, be it Sacred Harp, Gaelic Psalms, Sea Shanties or Old Chestnut Bawling in Singarounds at least require a certain expertise and familiarity with the idiom & songs before participation should be attempted, no matter now informal the context.

* An obvious chioce, but my knowledge of the idiom isn't so very extensive.