No, this is not here because “ever list needs a Christmas song” (and, really, that's very much a Christian perspective, why not a Hanukkah song, or something Hindu or Islamic?), this is here for another, very important reason: my father.
Despite my pantheistic statement above, I grew up in a “Christmas Christian” household, and even then, our celebrations were devoid of any religious aspects, except for grace at the Christmas dinner table when my Anglican grandmother attended. Where the lines blurred was with Christmas music.
I don't know if it was because the wealth of secular Christmas holiday music had yet to arrive when I was a kid (certainly, there wasn't much on the radio back then, other than Frosty the Snowman and Rudolph the Red-Nosed Reindeer) or just that my family didn't listen to anything else. I do recall, however, the grinding-click of my father's six CD changer (loaded in a cartridge that was no small feat to load and unload without getting fingerprints on discs), popping in the music from King's College, Cambridge.
When he was young, my father had been in the local church's choir. He was known for his ability to sing Christmas music quite well, to the point where he acquired the nickname “Deacon” at work. One of his favourite times of the year was Christmas, because it gave him the excuse to pull out the choir music and turn the volume up. In particular, I remember him singing Hark! The Herald Angels Sing.
My sister and I debate on whether or not this was his favourite Christmas song — or even his favourite album to play — but I remember it all the same. I remember him being in the kitchen making sausage rolls, belting out the song as if he were in the choir itself, vibrato and all. It is one of my most cherished memories of being a kid at Christmas, moreso than presents or the snow or maybe even the cookies (though, food is a tough one to overcome).
This was my introduction to choir music and to church organs, for which I've also got a certain appreciation. It led to me (along with significant cajoling from my friends) to joining the high school choir in my final year, and why I still love Christmas music.
But this song still holds a particular place for me. My father died nearly 20 years ago. Every Christmas, I ensure this song gets played at least once. Every Christmas, I will stop what I'm doing when this comes on, and think of my father, of the Christmases past, of the massively loud family (and extended family) dinners, of the joy. I usually cry, not in sadness — for the love that was always there, and still is all these years later.