For a Thursday puzzle, this could have been a lot worse. I had some difficulties that made me think it was hopeless partway through, and I wanted to keep my streak going as long as I could. So I took it a little slower and go through it. I was as surprised as anyone.
I pulled out 5A Language in which a nutty person might be told “Yer bum’s oot the windae”: SCOTS because, um, what? My first instinct with “oot” was something to do with Canada. And because it’s all kinds of weird, I thought Newfoundland because Canada:USA::Newfoundland:Canada. Of course that doesn’t fit in this grid. So I figured it was across the Atlantic. GAELIC doesn’t fit and isn’t even right. I put IRISH in there, but that wasn’t working. Finally SCOTS worked. I knew it had to start with an S because 5D Flavor: Sp.: SABOR. I don’t like the SCOTS answer, but it fits, so credit to Will Shortz for making sure this is what was published.
I figured out the theme early, and without it, I’d have been totally lost.
In an unusual move, I’m presenting these in the order I solved them and not in numerical order.
7D Instrument featured in 36-Across: OBOE. It’s always oboe. Safe bet.
56A Like an unused air mattress: DEFLATED. A half-guess, and it looked OK, and it had EFLAT in it. The theme is about orchestral stuff and likely in the classical music genre.
36A Work suggested by this puzzle’s circled and shaded squares: BEETHOVENSFIFTH. I figured this has gotta be it. Just gotta be. I didn’t even have many crosswords for it. I also hoped that fifth was right.
2D Key to this puzzle’s theme?: CMINOR. I filled this out as I went. I started out with _M___OR. It’s A-G to start and either MINOR or MAJOR. I never remember which piece is in which key, but it usually resolves itself. Or I guess and make adjustments from there.
49D First name of this puzzle’s dedicatee, born December 1770: LUDWIG. Took me a little bit to remember dude’s first name.
44A Pudding flavor: FI(G). Because there weren’t enough squares for chocolate, vanilla, or swirl. The (G) is what matters here.
45A Big name in in-flight internet: (G)O(G)O: I like my free hour of internet with my T-Mobile plan. The (G) and (G) are important.
Beethoven’s Fifth starts G G G EFLAT.
Finished this one in 26:30.