ON CHRISTMAS Day 2020, when Covid restrictions were in force, I crept to the south door of Portsmouth Cathedral to hear the Christmas Day Gospel and the socially distanced and numerically diminished choir singing “O come, all ye faithful”. The opening verses were sung as a Gradual hymn before the Gospel, and the last verse, “Yea, Lord, we greet thee, born this happy morning. . .” after the Gospel.

David Willcocks’s organ accompaniment for this last verse is so powerful that, for some years now, it has triggered conversations on social media. In many choirs, it is known simply as “the chord”.

As I listened outside the porch on that bleak Christmas Day, I realised that the chord on “Word” (”of the Father”), is, for me, when Christmas happens. The chord itself is, I am told, a B half-diminished seventh, and it has been compared to the “Tristan” chord in Wagner’s opera, a step towards the atonality which has marked more recent music.

The effect in the Christmas hymn is to make the familiar melody completely strange. The congregation find that they are singing something they do not expect, and yet they are singing exactly the same note as in the earlier verses.

But the change in accompaniment changes the musical context, and, to me, alters the meaning. At this point, Christmas goes beyond our comforting expectations of warmth and good cheer, and becomes a crashing announcement of God’s descent into human flesh, God piercing the darkness of our senses, God disrupting our lives, our dreams and struggles and sufferings. In the moment of singing the last verse with Willcocks’s accompaniment, you cannot tell whether the chord represents the most disturbing thing you have ever heard, or the glorious resolution and resolve of all your worst fears — or both at the same time.

The chord sets alongside the human charm of the nativity scene the credal affirmation of Christ as “God from God, Light from Light, True God from true God, begotten not made. . .” It reminds me of the way in which some liturgical texts allude to Wisdom 18.14: “When all things were in silence and night was in the midst of her swift course, thine Almighty Word leapt from heaven.”

In the original context, the words continue “into the land that was doomed”; for the verse from Wisdom is referring to the plagues of Egypt, which “filled all things with death”. It is an extraordinary paradox that this doom-laden text would, in time, became a prophecy of the healing that Christ’s birth brings to the world.

But it is exactly that paradox that “the chord” represents. It spoke to me, in the Covid bleakness of 2020, and perhaps it still does, as we contemplate the ruin we have made of our world, and long, once again, for a redemption that goes beyond tinsel and crackers.