'Tis the season to be mum.
I remember, as a high schooler, going from house to house with my Sunday School class, serenading the neighbors with Christmas carols. (Between the houses we sang about three kings smoking a rubber cigar, but when in front of a house with a receptive family, the kings "from Orient" were and and they were "bearing gifts," not smoking a thing.)
This behavior of going from house to house to celebrate the season, singing songs and spreading cheer, dates back to the activities of the mummers in England who would take their celebration to the streets after Christmas carols were banned from the church in the middle ages. Besides singing songs, these street singers wore masks and put on plays. Songs like "Christmas is a-coming, the goose is getting fat, please put a penny in the poor man's hat" expressed the desire of the entertainers to be paid for the show (is it any different when we were invited in for hot chocolate and Christmas cookies?). The caroling usually occurs early in advent, and often those being serenaded end up joining in with the singers.
The term "carol" actually refers to a song used to accompany dancing, so the tradition of adding drama to the singing does make sense. Each country/culture has its own tradition of going house-to-house to spread the holiday cheer. "Santa's Net" is a website that covers different traditions by culture, an interesting place to start to learn about the caroling, and other holiday behaviors, that your ancestors may have engaged in.
Other well-known songs about the house-to-house tradition are "Here We Come a-Wassailing" (which I recorded on my CD Songs of Holidays Past), "a-Soalin'" (made popular by Peter, Paul, & Mary), and "The Wren" (made popular by the Clancy Brothers).
So, whether your Christmas carol tradition involves the house-to-house caroling, joining with friends in a living room by a crackling fire, raising voice in song with choirs at a church service, or just humming along with the stereo (or MP3 player), you are carrying on an ages-old tradition; one your Christian ancestors probably enjoyed, too. So don't keep mum! Raise your voice in holiday song!