Melissa here. In 1921 Edward Elzear "Zez" Confrey wrote his novelty piano solo Kitten on the Keys, inspired by hearing his grandmother's cat walk on the keyboard of her piano. It became a hit, and he went on to compose many other pieces in the genre.
Across:
1. Breaks in relations: RIFTS.
6. Update cartographically: REMAP.
11. Adorns with Charmin, for short: TPS. Toilet papers, as a verb.
14. Basketball Hall of Famer __ Thomas: ISIAH.
15. Sherlock Holmes' younger sister as depicted in a recent Nancy Springer book series: ENOLA.
16. Hot temper: IRE.
17. Using any available means: CATCH AS CATCH CAN. One of two grid-spanners.
20. He broke Babe's record in 1974: HANK.
21. Tulip-to-be: BULB.
22. Kitchen protection: MITTS.
23. Rocks in a bar: ICE. For drinks.
24. "Miss Saigon" setting: NAM. Vietnam. Miss Saigon is a coming-of-age stage musical by Claude-Michel Schönberg and Alain Boublil, with lyrics by Boublil and Richard Maltby Jr. It is based on Giacomo Puccini's 1904 opera Madame Butterfly, and similarly tells the tragic tale of a doomed romance involving an Asian woman abandoned by her American lover.
25. Clear out: VACATE. Hit the road, Jack.
26. A college applicant may have to write one: ESSAY.
28. City on the Ruhr: ESSEN. City in Western Germany.
31. Roman 151: CLI.
32. Ella's forte: SCAT.
34. Strain: TAX.
35. Swiss Army knife's assortment: USES.
36. Dashboard gauges: ODOMETERS. An instrument for measuring the distance traveled by a vehicle.
39. Go for a rebound: JUMP. Rebounds in basketball are a routine part in the game; if a shot is successfully made possession of the ball will change, otherwise the rebound allows the defensive team to take possession. Rebounds are also given to a player who tips in a missed shot on his team's offensive end. A rebound can be grabbed by either an offensive player or a defensive player.
42. Generation __: GAP.
43. Opportunity metaphor: DOOR.
45. Ike's WWII command: ETO. European Theater of Operations.
46. Heathcliff's love: CATHY. Wuthering Heights.
48. Future docs' exams: MCATS. Medical College Admission Tests.
51. Cassiterite, e.g.: TIN ORE. Cassiterite is a reddish, brownish, or yellowish mineral consisting of tin dioxide. It is the main ore of tin.
53. A-lister: VIP. Very Important Person. Well, excuse us.
55. Govt. mortgage agcy.: FHA.
56. Golf goof: SLICE. A slice is a ball that curves away from the players dominant hand.
57. Slangy sweeties: BAES.
59. Stern's opposite: STEM. Nautical terminology.
63. Skater Midori: ITO.
64. Old Venetian coin: DUCAT. At today's gold prices, one ducat is worth $148.83.
65. Havana's __ Castle: MORRO. A fortress guarding Havana Bay, Cuba.
66. Leb. neighbor: SYR.
68. Elizabeth of "WandaVision": OLSEN. Miniseries on Disney+.
1. Singer Lionel: RICHIE. Blast from the past.
2. Jason of "Harry Potter" films: ISAACS. Played Lucius Malfoy.
3. Exercise goal: FITNESS.
4. Thumb-pressed nail: TACK. Thumbtack.
5. Theater rebuke: SHH.
6. Continue: RESUME.
7. Ltr. insert: ENCL. Enclosure.
8. Utah city with a Biblical name: MOAB.
9. __-rock: music genre: ALT. Alternative rock is a category of rock music that emerged from the independent music underground of the 1970s and became widely popular in the 1990s.
10. Game with ghosts and a maze: PACMAN. Pacman doodle. Use your arrow keys to play.
11. Tiny breath mints: TIC TACS. Remember this scene with Patricia (Parker Posey) in You've Got Mail?
12. Talk nonsense: PRATTLE.
13. Martial arts instructors: SENSEIS. Teachers.
18. Attorney's gp.: ABA. American Bar Association.
19. Juice box brand: HI-C.
24. Long-distance swimmer Diana: NYAD.
25. Perturbed: VEXED.
27. "Rent-__": 1988 film: A-COP.
29. Curry of the NBA's Warriors: STEPH.
30. Warmed the bench: SAT.
37. Yoga surface: MAT.
38. Frolic: ROMP.
39. Kawasaki watercraft: JET SKIS. Personal watercraft.
40. The U in "SUV": UTILITY. Sport Utility Vehicle.
41. Hall pass checker: MONITOR.
44. Roof supports: RAFTERS.
46. Belief systems: CREEDS.
47. "The Big Fib" host __ Nicole Brown: YVETTE. Game show on Disney+.
49. "And __ off!": THEY'RE.
52. Fall mo.: OCT. October.
54. Suffix like -like: ISH.
57. Fla. resort: BOCA.
58. Toilets for T.S. Eliot?: Abbr.: ANAG. Sneaky. Toilet is an anagram of T.S. Eliot.
61. Trail mix morsel: NUT.
62. Fall Out Boy genre: EMO.