I don't know who, exactly, I was expecting to do these celebrity puzzles, but it wasn't Emanuel Ax! He just went up a few notches, and he was already up there.
This was a fun one that I thought was a themeless until I hit the revealer, way off in the SW - 52D: Word that can follow the ends of 20- and 54-Across and 4- and 26-Down (NOTE). That gives "mash note," "sour note," "half note," and "high note." We also have the lovely eighth note in the center. Nice touch.
I like all the theme answers, but I was not familiar with the term "mash note." I thought it might be something that whiskey reviewers talk about when explaining the various flavor profiles... but no, it's a raving fan letter, or maybe a love/stalker letter - I'm still not entirely sure. The others are well known to me. I also like the nod to Mr. Ax's instrument in 32A: What the keys are to a pianist? (PLAYAREA). Ha!
There are some pretty questionable entries - EREI, LIENEE, UVRAY, and a few others, but I think that the theme and the fun material far outweigh them today. QUAKERGUN (11D: Log painted deceptively to look like a cannon) is a new one to me, but I love it! VICUNA (42A: Andean animal with expensive wool) is quite exotic, and MANGIA (35A: Trattoria order?) is hilarious. For those who speak Italian, anyway.
1A: BBQ platter side (SLAW) - B-. Interesting word.
Favorite: ANECTDOTAL (34D: Not statistically based, as evidence). I just like this one.
Least: NCAR (55D: Nascar Hall of Fame locale: Abbr.) - Yikes.
Overall, thumbs up.