Theme: Pep Rally - Combine the ends of the theme entries and you get the unifier.
20A. The smile on an email happy face : PARENTHESIS
37A. Barrier-breaking noise : SONIC BOOM
56A. Exalted group leader, facetiously : GRAND POOBAH
65A. Encouraging cry, such as the one formed by the ends of 20-, 37-, and 56-Across : CHEER
Argyle here. Today's constructor passed away in January. C.C. interviewed him in April, 2010. link. Scroll the comments to see his take on his family's name.
Today's theme may have been hard to suss without the unifier. Certainly, some of the entries harder than normal Tuesday's but do reflect Gary's interests; bridge, jazz, sports, etc. But like all puzzles, I have found one man's Natick is another man's gimme.
Triple seven letter files in all four corners.
Across:
1. __ Tomé and Príncipe : SÃO. The Democratic Republic of São Tomé and Príncipe, is a Portuguese-speaking island nation in the Gulf of Guinea. Map.
4. Cap on spending, say : LIMIT
9. Norwegian Sea arm : FJORD
14. Footed vase : URN
15. Habituate : ENURE
16. Friend of Fido : ROVER. "Woof!"
17. Agt.'s cut : PCT. (%)
18. Grouchy Muppet : OSCAR
19. The other side : ENEMY
23. Director Reiner : ROB
24. Jazz singer Anita : O'DAY. Skylark(3:07)
25. Vatican City is one : ENCLAVE
27. Split end in a uniform : RECEIVER. A football player that lines up apart from the formation.
32. Air-conditioned : COOLED
33. Tut's cousin? : "TSK!"
34. Andrea __: ill-fated vessel : DORIA. Collided with the MS Stockholm in 1956 off the coast of Nantucket, MA. The Wikipedia article is interesting in how the sinking was handled, given the recent Costa Concordia event.
36. 88 or 98 automaker : OLDS. Not only your father's Olds but your grandfather's, too. Bill Haley and his Comets sing about his "88". Clip.
40. "Pygmalion" playwright : SHAW. (George Bernard Shaw)
43. Reeves of "Speed" : KEANU. Movie with co-star Sandra Bullock.
44. Palindromic Altar : ARA. A southern constellation situated between Scorpius and Triangulum Australe. Which ties in with 42-Down. Supergiant in Scorpius : ANTARES. Antares is a star in the constellation Scorpius.
47. Bridge holding such as ace-queen : TENACE. Nothing to do with TEN ACE. Derived from the same root as TONGS and indicates a pair of cards that is missing the intervening card.
50. Surprises : STARTLES. Verbs.
52. More decrepit : RATTIER
54. Wuss : WIMP
55. Topsy's playmate in "Uncle Tom's Cabin" : EVA
61. __ cotta : TERRA
63. Household cleanser : BORAX. Still available, I believe. 20 Mule Team® Borax
64. Alternate identity letters : AKA. (also known as)
66. Trumpet sound : BLARE
67. __ canto: singing style : BEL. BEL canto (Italian, "beautiful singing") is an Italian opera term. It has several different meanings and is subject to a wide array of interpretations.(per Wikipedia)
68. Leno and Letterman, e.g. : HOSTS. If you're up late.
69. Artist Grant Wood, by birth : IOWAN. So maybe American Gothic were his neighbors.
70. Bermuda hrs. : AST. Summer hours would be ADT (Atlantic Daylight Time)
Down:
1. Provide for, as a dependent : SUPPORT
2. Teen haunts : ARCADES
3. According to plan : ON TRACK
4. Ponce de __ : LEON. He led an expedition to Florida, looking for the Fountain of Youth. And still they come.
5. R&D site : INST.. (institute, such as RPI, Rensselaer Polytechnic Institute)
6. A whole lot : MUCH
7. "Dies __": Latin hymn : IRAE. (Day of Wrath)
8. Short and sweet : TERSE. Not necessarily sweet but you get the point.
9. Mural on wet plaster : FRESCO
10. Comedian Lovitz : JON. Feel free to link your favorite clip.
11. From one end to the other : OVERALL
12. Took out : REMOVED
13. Ditches where creeks once were : DRY BEDS. Oddly clued.
21. A patch may cover one : EYE
22. Co. designation : INC. (incorporated)
26. Rise up dramatically : LOOM
28. Courtroom oath : "I DO". Swear to tell the truth.
29. Otto __ Bismarck : VON. (1815–1898)
30. The Phantom of the Opera : ERIK
31. Puts through a food press : RICES
35. Blind as __ : A BAT
37. Babe Ruth's sultanate? : SWAT. Just one of his nicknames was The Sultan of Swat, coined by sportswriter, Warren Brown.
38. "I'm __ roll!" : ON A
39. Wilder's "__ Town" : OUR
40. Final race leg : STRETCH
41. Bum's rush : HEAVE-HO
44. Woodcutter who stole from thieves : ALI BABA
45. New versions of old films : REMAKES
46. Paving material : ASPHALT
48. Perfectos, e.g. : CIGARS
49. Suffix with profit : EER
51. Pair : TWO
53. Jewish holy man : RABBI
57. __ contendere: court plea : NOLO
58. Shootout shout : "DRAW!"
59. Lawyer's aide : PARA. Shortened from paralegal.
60. Plow pullers : OXEN
62. Inactive mil. status : RET. (retired)
Argyle