Rewatch aaaaaaa
Sweet holy fuck I can't put into words how much I love this episode.
It's like the opposite story of Green Isn't Your Color; same character dynamics in play, same mental obstacles to deal with, but in this case instead of being a story about Fluttershy going along with something she doesn't want to do out of a misguided sense of loyalty or demureness, now it's about Fluttershy indulging in a pursuit that she genuinely enjoys but that is as
dangerous—to her—as a rock climber tackling El Capitan. She's putting her mental well-being at risk, in a form of thrill-seeking that is meaningful only to someone like her for whom dabbling with mortal danger means something like "appearing on stage".
The interplay between Rarity and Fluttershy is that much more in-depth given their long history together; Rarity cottoning on to what's going on in Fluttershy's head (both when she defers to Fluttershy's wishes not to peform, and later when she realizes that Fluttershy is begging to be given the spotlight now that there's a way she can deal with it) is something that the self-absorbed Rarity of GIYC would probably not have done so readily. She's still Rarity, of course, but she's grown from having had to accommodate her friend for so long. And this is a new wrinkle in their relationship, something they haven't experienced before.
I simply cannot say enough good things about the song. I mean god
damn. Musically and lyrically, it is head-and-shoulders above 95% of the rest of the songs in the show in terms of both ambitiousness and in the skill of its execution. It's just freaking beautiful to listen to; it's well constructed and the music is both exuberantly simple and cleverly surprising. It's even got a lyrical theme that underlines Fluttershy's state of mind every time she sings it; whenever she says "I've got the music in me", it's a recapitulation of the fact that stage fright or not, she
loves to sing and is really good at it, and she's pining for a way to express it that doesn't clash with her psyche. I don't know how the team was able to come up with something so uncharacteristically rich and stylistically correct
and innovative, whether it's Amy Keating Rogers doing overtime on the barbershop research beat, or if this was a matter of Ingram arranging the hell out of things and pulling together a quartet that could rock the hell out of their performance (I think AKR probably did the heavy lifting, since a lot of the surrounding writing—like Rarity complaining about how she'd have to rearrange the parts—sounds like it comes from someone with a well-established musical composition background in her own right). But however it came together, the whipped cream on top of it is the reprise at the end that manages to fold in Fluttershy's own little trees-and-flowers song from the beginning, and make it all feel like a natural fit even though the two songs didn't start out very similar at all.
The song also has what has to be one of the top five moments in the entire show for me, the moment where Fluttershy realizes to her own astonishment that she really really loves what she's doing:

I mean you even see the tip of her hair curl up to punctuate it,
oh my gooooooood 
Dear fucking god the whole main first run-through of the song is just such a beautiful experience. The fact that they give it all plenty of time to breathe and play out, that we get to hear the
entire song and not just a clip as part of a montage, is just such a bonus—storytelling-wise they could have cropped it down into a shorthand version of what we in the audience would have realized was just a stand-in for what the full-length song would have sounded like, and the impact (emotionally and musically) would have been sorely reduced. But as it is, you get both barrels right in your face, and the song is
genuinely every bit as good as the on-screen audience is acting like it is, which is such a rare treat in any cartoon.
The only gripe I have about it is kind of a weird one. Big Mac/Fluttershy has the opening stanza, obviously; but then, the second stanza has the blue tenor guy stepping out to do his own solo. But the soloist
voice I could swear is a female alto. I've listened to it several times now and I just can't hear it as anything other than that they
meant for the other female singer (not Rarity) to have that line, but the animators gave it to the blue guy (whose real tenor voice you can hear pretty clearly in other parts of the song).
Song aside: there are a lot of interesting tableaux/establishing shots, particularly surrounding the pet fair (which I love from a worldbuilding perspective; the idea that the ponies would have a fair in which random attendees would get to go up to booths and play with seals and turkeys and deer and decide who they might want to adopt into a horse household is just so delightfully goofy). Lots of ponies in the background wandering around and decorating things, but surprisingly few visual gags. It's a lot of ambient action but no
jokes. Very interesting atmospheric choice. I kept wondering whether I was supposed to be looking for things to giggle at, but all I ever found was that weird OC guy and his daughter. (Seriously WTF)
Pinkie, I dunno, I thought she was funny, and the fact that they kept lampshading and calling out how inappropriate her behavior was defangs the arguments against her for me. As for her screechiness, it was interesting that it was actually set up intentionally that way here—Pinkie's very first line, when the ponies hear comment on Fluttershy's singing, was "Singing with the MOST BEAUTIFUL VOICE!

" —which I think was an intentional inside riff on the fact that it was Andrea Libman delivering that line, in what is meant to be as much of a contrast with Fluttershy's sweet and melodious voice as possible. She's
trying to sound like the anti-Fluttershy there, and that theme just carries over throughout the rest of the episode.
Random: the out-of-the-blue Matrix bullet-time effect when Fluttershy tosses the seeds in the air

Also the little rapid-fire scene between Applejack and Big Mac where she instantly guesses the entire course of events and all he has to say is "eeyup" and "nope"—I can't believe they're still coming up with new ways to play with that schtick and keep it actually funny.
I'm a bit iffy on the scene where her friends
logic Fluttershy into submission about how much she
must have enjoyed performing, because weren't the screaming fans and all the adoration
just great? I mean, maybe the answer is still
no, right? Maybe Fluttershy really seriously can't deal with that much of that kind of attention, even
if she enjoys the Zen-like experience of singing with a group. These are subtle interactions of mental stimuli, and someone like Fluttershy surely is packed full of competing impulses that fight with each other all the time. The imagery of spotlights that conflate the adoration of stardom with being chased down an alley by police are very clearly playing off this theme; and it's a little bit disappointing to me that the story kind of gives up on that thread by having Fluttershy just
give in to her friends' prodding rather than making them understand that even still, even now, she
really just doesn't like being on stage in front of people, and no amount of logic and common sense and shaming is going to change that. In the end she's up there triumphantly singing, and the end result of the lesson seems to have kinda gone off into the weeds a bit, with the message being "Hey, just get over it, it's all in your head, you'll thank us later".
But that's a small thing. Overall, damn: best episode of Season 4 for me by a long way, and definitely some of the show's best work ever. It's the kind of thing I'd unhesitatingly show a newcomer, if it weren't for the reliance on the Bridle Gossip callback. (Incidentally even Zecora's part is really good; she had some excellent and organic-sounding rhymes, way better than some of her other more wacky appearances, some of which AKR was also responsible for.)
E: I hadn't noticed this before, but early on when the Ponytones are rehearsing, Fluttershy is singing along with them while she sets up birdhouses. At least for a moment, until she thinks people are watching
