Christmas Carol Quiz

These are popular Christmas carols. Can you figure out their normal names?

1. Approach everyone who is steadfast.
2. Ecstasy toward the orb.
3. Listen! The Foretelling spirits harmonize.
4. Hey, Minuscule urban area southeast of Jerusalem.
5. Quiescent Nocturnal period.
6. The Autocrat troika originating near the ascent of Apollo.
7. The primary carol.
8. Embellish the corridors.
9. I'm fantasizing concerning a blanched yuletide.
10. I apprehended my maternal parent osculating with a corpulent unshaven male in crimson disguise.
11. During the time ovine caretakers supervised their charges past midnight.
12. The thing manifests itself at the onset of a transparent day.
13. The coniferous nativity.
14. What offspring abides thus?
15. Removed in a bovine feeding trough.
16. Creator, cool it, you kooky cats!
17. Valentino, the roseate proboscises wapiti.
18. The slight percussionist lad.
19. Father Christmas approaches the metropolis.
20. Seraphim we aurally detected in the stratosphere.

(Don't read the comments until you try to answer them yourself. I have put the answers in the comments.)