I would describe this as a 3-part arrangement, with 2 optional extra harmonies. Sometimes, the 2 harmonies in the 3-part version, have a different rhythm to the tune, so they need a little time to learn, but are quite easy. The 2 extra harmonies, in the 5-part version have a different rhythm again and therefore, although they’re not especially complicated in themselves, they do make the whole song longer and more complex to teach and learn, hence I’ve categorised the 5-part version as moderate.
The origins of this carol are unknown, but it became popular from 1935, when it was arranged by Bristol-based composer Arthur Warrell. I wanted to create a ‘jolly’ arrangement, which would be pretty easy to learn, so that groups wouldn’t have to start working on it months before the festive season! I nearly always stick with the 3 part version for that reason, but I couldn’t resist adding 2 more, optional parts, to add extra texture and rhythm, either for performances or to give regular groups something to add, to keep the interest going after a few years of singing it!