Why are so many Christmas carols in harmonic/melodic/natural minor, or dorian?

Question

Off the top of my head, entirely in minor or dorian, there's God Rest Ye Merry Gentlemen, What Child Is This?, Sing We Now of Christmas, Carol of the Bells, O Come O Come Emmanuel... O Holy Night spends time in minor, as does It Came Upon the Midnight clear.

So if Christmas is supposed to be happy, why all the minor?

My theory is that these carols were written by liturgical writers, and that the aeolian and dorian modes simply used to be more popular, especially with the church. This is reinforced by the fact that the carols in major tend to be secular, while the ones in minor are almost always about Christ... but does anyone have a real explanation for this phenomenon?

Answer 1

Excellent question, and your theory may be right. You might also wonder why practically every Jewish song, even happy ones, are in the minor key.

I think the minor key brings about the solemnity and seriousness of the situation. One: you have a baby born in harsh circumstances, in a stable, laid in a manger, in a crowded city. Two: you have God coming down in human flesh in order to save sinful humanity from itself. Pretty heavy stuff if you ask me.

Then again, we do have Joy to the World, Silent Night, Do You Hear What I Hear?, O Come All Ye Faithful, and other religious carols in major keys, expressing the joy of a new birth and the relief that the Messiah has come at last.