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Caroling has always been one of those things that seems like a good idea when you see it in movies or on TV but never really works out the way you want in real life. I remember going caroling with my youth group when I was young, and while I enjoyed the singing, I felt like the visit and the gift we brought was more meaningful to the people than the songs we sang. Maybe they enjoyed it, but I feel like some people would rather skip the unsolicited singing and just invite people in for a chat. Then, if they asked for it you could leave them with a song, but if they didn't you could just leave them with a hug and a warm feeling. That said, maybe these days people would be more likely to just sing outside and not go in given certain safety concerns.
In this case, a visit from a nice dog on Christmas Eve is probably more enjoyable for the woman than hearing people sing, especially when you add in what I imagine is questionable guitar playing. Besides, given that Uncle Elby describes her as "that attractive widow" implies what he really wants is to win her affection more than to make the season brighter for her.