Theme: Two Different Words That Start With The Same Two Letters - La/La
20A. *Teaching aid for learning foreign tongues: LANGUAGE LAB
59A. *Deep blue gemstone: LAPIS LAZULI
5D. *Superboy's girlfriend: LANA LANG
11D. *Satisfaction after setbacks: LAST LAUGH
35D. *Cowboy star with a bullwhip: LASH LARUE
41D. 2016 Best Picture (no, wait; it wasn't!) ... and a fitting place for the answers to starred clues?: LA LA LAND
Argyle here. All the other letters except J and Q. Entries in rows: 2, columns: 4. Cute reveal.
Across:
1. Place for wet cannonballs: POOL
5. Volcanic rocks: LAVAs
10. Move like a river: FLOW
14. Vineyard unit: ACRE
15. Plant used in tequila production: AGAVE
16. Spencer of "Good Morning America": LARA
17. Really wiped out: BEAT
18. Private's denial: "NO SIR!"
19. Like many resold items: USED
23. Tot's piggy: TOE
24. Like an accurate hockey shot: ON GOAL
25. Arbor Day month: APRIL
27. Brute: BEAST
30. Tackled, as a task, with "at": HAD A GO, hopefully done...
33. With competence: ABLY
36. Orderly: NEAT
38. "__ I lie to you?": WOULD
39. Spy org. created under Truman: CIA. (Central Intelligence Agency)
40. Appetizer often served with duck sauce: EGG ROLL
42. Prefix with centric or caching: GEO
43. Dermatologist's surgical tool: LASER
45. "__ girl!": ATTA
46. "Believe" singer: CHER. The song featured audio processor software, Auto-Tune, which became known as the "Cher effect".
47. Theater guides: USHERs
49. Sun-related: SOLAR
51. Plunders: LOOTS
53. Died down: ABATED
57. Place to de-stress: SPA
62. Angelic glow: AURA
64. Dreadlocks wearer: RASTA
65. "__ la Douce": IRMA. (1963 romantic comedy starring Jack Lemmon and Shirley MacLaine)
66. Essential point: CRUX
67. Promotional connection: TIE-IN
68. Black, to a poet: EBON. Shakespeare's jet?
69. Ship's backbone: KEEL
70. Mortimer on Bergen's knee: SNERD
71. See 63-Down: ROSE. 63-Down. With 71-Across, rocker whose first name anagrams a West Coast airport code: AXL. (LAX / Los Angeles Airport)
Down:
1. Picasso who painted Gertrude Stein: PABLO
2. Arctic or Indian: OCEAN
3. Sumatran ape: ORANG. (orangutan)
4. Allow to pass: LET GO BY
6. Intensely excited: AGOG
7. Ming museum piece: VASE
8. Hometown of St. Teresa: ÁVILA, in 52-Down. Iberian Peninsula country: SPAIN
9. High-ranking angel: SERAPH
10. Winter ailment: FLU
12. Layered cookie: OREO
13. Get one's tootsies wet: WADE
21. Dubai's fed.: UAE. (United Arab Emirates)
22. Saloon slugfest: BRAWL
26. Altar words: I DO
28. Sonic the Hedgehog game company: SEGA
29. Small fruit pies: TARTs
31. Pure joy: GLEE. Eating tarts.
32. What the nose knows: ODOR
33. Civil rights gp.: ACLU. (American Civil Liberties Union)
34. Skewed view: BIAS
37. Terrier on the Yellow Brick Road: TOTO. Not in Kansas.
40. Filmdom's Flynn: ERROL
44. Fair-hiring letters: EEO. (Equal Employment Opportunity)
46. Comparatively outlandish: CRAZIER
48. Inaugurates: STARTS
50. Case workers' org.?: ABA. (American Bar Association)
54. Supercharger: TURBO
55. "St. __ Fire": ELMO'S
56. "Cheers" waitress: DIANE. (Shelley Long) Different bar from 50-Down.
57. Potato holder: SACK
58. Like 24-karat gold: PURE
60. "__ skies of blue and clouds of white ... ": "What a Wonderful World": I SEE
61. Recipe instruction: STIR
Argyle