This is a (somewhat euro-centric and biasedly seasonal) Mystery of the Missing Middle quiz. The challenge is to identify a well-known melody from a skeletal accompaniment (which isn't the original one, could be surrounding the absentee melody in any fashion and might even be contrapuntal so that it appears to stand as a tune in its own right).

There are anonymised GIF images to view and play (if you have a minimally competent keyboard player or a pair of treble and bass instrumentalists to hand: eg flute & trombone, oboe & bassoon, violin & cello); and, for the more musically challenged, MIDI files to download and hear.

1. GIF … MIDI
2. GIF … MIDI
3. GIF … MIDI
4. GIF … MIDI
5. GIF … MIDI
6. GIF … MIDI
7. GIF … MIDI
8. GIF … MIDI
9. GIF … MIDI
10. GIF … MIDI
11. GIF … MIDI
12. GIF … MIDI
13. GIF … MIDI
14. GIF … MIDI
15. GIF … MIDI
16. GIF … MIDI
17. GIF … MIDI
18. GIF … MIDI
19. GIF … MIDI
20. GIF … MIDI
21. GIF
22. GIF
23. GIF
24. GIF
25. GIF
26. GIF
27. GIF
28. GIF
29. GIF
30. GIF
31. GIF
32. GIF
33. GIF
34. GIF
35. GIF
36. GIF
37. GIF
38. GIF
39. GIF
40. GIF

PS Don't read any comment threads here unless you're prepared to be spoiled (because there is no simple way of concealing people's guesses).

PPS The latest batch includes some which are more commonly American in usage and some which are more obscure.

PPPS Now that most solstice celebrations are over (though not all versions of the new year), the solutions are available in comment form in the test view of the page.