Theme: Name That Tune - Probably the first song we ever learned.
20A. "Twinkle, twinkle, little star" : ABCDEFG
28A. "How I wonder what you are" : HIJKLMNOP
36A. "Up above the ..." : QRS
41A. "... world so high" : TUV
44. "Like a diamond in the sky" : WXY AND Z
58A. Ditty sharing a melody with "Twinkle, Twinkle, Little Star" : THE ALPHABET SONG
Argyle here. The puzzle has mirror (left to right) symmetry and is a pangram. Plus: the reveal spans the grid.
Across:
1. Gallery exhibitors : ARTISTS
8. NFL great "Boomer" : ESIASON
15. Dada pioneer : JEAN ARP
16. Heavenly : SUBLIME
17. "Hamlet" woman at whose grave Gertrude says "Sweets to the sweet" : OPHELIA
18. Flowing locks : TRESSES
19. Rain-__ Pops: gum-filled candy : BLO
22. LAPD rank : SGT.
23. Polite country assent : YES'M
25. Language suffix : ESE
26. "Divine Secrets of the __ Sisterhood" : YA-YA
31. First of 12 popes : PIUS I
33. Mark or markka replacements : EUROs
37. Rock bottom : NADIR
43. Carrier with a hub at DEN : UAL. Denver is the fourth-largest hub for United Airlines.
46. Brewed drink : TEA
47. Very little, in recipes : A DASH
49. Put the kibosh on : END
50. Agenda listings : ITEMS
52. "Divine Comedy" poet : DANTE
53. Cagey : SLY
54. "Gay" capital of song : PAREE
55. Forest foragers : DEER
57. Finger of smoke : WISP
65. New Year's Eve popper : CORK
66. Gumption : MOXIE
67. Fencing sword : EPEE
68. Untidy situation : MESS
69. Throw money around : SPEND
70. Atty.-to-be's exam : LSAT. (Law School Admission Test)
Down:
1. "This looks like __ for Superman!" : A JOB
2. Email option : REPLY
3. California/Nevada resort lake : TAHOE
4. Suffix with elephant or serpent : INE
5. Deli display : SALAMIs
6. Chicago paper, familiarly : TRIB. Chicago Tribune
7. See 12-Down : SPACEK 12D. With 7-Down, "Coal Miner's Daughter" star : SISSY
8. Hold in high regard : ESTEEM
9. Poke around the Web : SURF
10. Pleading remark : "I BEG YOU"
11. Racing Unsers : ALs
13. Horseshoe-shaped letter : OMEGA
14. Place for a jay : NEST
21. ISP option : DSL. (digital subscriber line)
24. Moo __ pork : SHU
27. Busy mo. for a CPA : APR.
29. Hex : JINX
30. Many a Pi Day celebrant : NERD. Pi Day is March 14 (or 3/14) celebrating the mathematical constant π since 3, 1, and 4 are the first three significant digits of π.
31. Big name in high fashion : PRADA
32. 1980s four-peat Stanley Cup champs : ISLANDERS
34. Frozen fruit-juice treats : OTTER POPS
35. "I was wrong. So what" : "SUE ME!"
36. Campus hangout : QUAD
38. Yeses at sea : AYEs
39. Pioneer Boone, folksily : DAN'L
40. 200-lap race, briefly : INDY. Indianapolis 500.
42. Place for posies : VASE
44. Ferris __ : WHEEL
45. "Shh!" : "ZIP IT!"
48. Chophouse fare : STEAKS
51. Loafer adornment : TASSEL
56. Tach measures: Abbr. : RPMs
57. Invasive plant : WEED 59D. 57-Down killer : HOE
58. Channel for old films : TCM. (Turner Classic Movies)
60. Short flight : HOP
61. Lumberjack's tool : AXE
62. Composting receptacle : BIN
63. PBS supporter : NEA. (National Endowment for the Arts)
64. Understand : GET
Argyle
