If Handel's Messiah is the quarterback of holiday music, Bach's Christmas Oratorio remains the second-string walk-on. But this Sunday, Dec. 23 at 10 am, WQXR gives Bach's underplayed work a starting spot in the lineup with a complete broadcast of the piece.

Unlike the moody Messiah (whose final third is based on the Anglican burial service), the Christmas Oratorio is completely about Christmas. It is also a sprawling work, comprised of six cantatas meant to be performed from Christmas to Epiphany. The whole runs some two-and-a-half hours, significantly longer than Messiah, and yet it spotlights the German composer at his best, with intimate arias, colorful instrumental pieces and uplifting choruses.

Tune in for a recording by the Academy for Ancient Music Berlin and RIAS Chorushamber Choir led by Rene Jacobs.

Below, host Jeff Spurgeon gives us five things to listen for in the oratorio.

→ Read the texts for Part I, Part II, Part III, Part IV, Part V and Part VI (all in English and German).

1. First things first: What's an oratorio? And what makes this one stand out?

2. How – and why – Bach recycled from cantatas in the Christmas Oratorio:

3. What the words mean, and where they come from:

4. The role of the oboe: With all those shepherds in the fields keeping watch over their flocks, the oboe comes in handy, representing the shepherds’ pipes:

5. How Bach used a German baroque cradle song in the Christmas Oratorio. It is the longest single moment in the entire piece, and certainly one its high points.