Christmas Carols: Tomorrow shall be my dancing day
Based on the first verse of this song, it doesn't sound much like a Christmas carol at all:
Tomorrow shall be my dancing day;
I would my true love did so chance
To see the legend of my play,
To call my true love to the dance.
Sing O my love, O my love, my love, my love,
This have I done for my true love.
The next verse makes things pretty clear, given that it starts "Then was I born of a virgin pure . . ." and the following nine verses continue to tell the story of Christ's life. Still, it doesn't really explain who Christ is addressing as His "true love" and what this "dancing day" is, exactly.
According to the New Oxford Book of Carols, the idea of Christ addressing humankind as His true love has its roots in "higher medieval poetry," continuing in the tradition which interprets the Song of Solomon as a figuratively expressing Christ's love for the Church. Judging by the last verse:
Then up to heaven I did ascend,
Where now I dwell in sure substance
On the right hand of God, that man
May come unto the general dance.
The dance is a metaphor for Heaven or Paradise. Incidentally, some sources think that this carol may originally have been part of a dramatic cycle telling the story of the life of Christ. (Hence the line "to see the legend of my play.")
I was originally familiar with one setting of this carol (the first one, linked below) and also found two other arrangements while I was looking around for good recordings.
Birmingham Children's Choir, December 2008:
Choir of King's College, Cambridge, John Gardner setting, 2007(?):
Belfast Choir (with an inexplicable James Bond intro?!), 2007(?):