Gregorian chants tend to give me homicidal thoughts. Granted, I don’t hear them very often, that’s just a sign they could disappear completely and not be missed.
It’s funny that the OP is about a segment within a musical, yet I’m apparently the first to say, just musicals in general. I would be fine if all musical theatre completely disappeared.
Never been able to dig it. No matter how cool the musical supposedly is, the music always sounds like “musical music” and not like “real music.”
Edit - some of the songs in Grease, like Hopelessly Devoted to You, and Those Magic Changes are really great, just as standalone songs. But that’s a very rare exception for me. Can’t think of ANY other musical songs that do anything for me.
Scat singing.
I’m going to agree with this for the most part. In the early and mid 20th century there were a lot of songs originally released as part of a musical that qualify as “real” music—Cole Porter songs for example.
But by the time we get to Andrew Lloyd Webber, you have a style of song that can’t stand on its own.
That’s number two on my list.
mmm
Flute jazz.
Is that the sequel to two girls and a cup?
It’s funny, because The Who’s Tommy is one of my all-time favorite albums, yet even I will admit that parts of it border on “musical music.” But it’s like it doesn’t go all the way. It approaches the border, but doesn’t cross it.
iswydt 
Well, what else are they? They’re basically performance troupe events involving specified types of physical activities that have to follow certain rules of form but also allow for a lot of unscripted improvisation.
If, for example, improv theater or unscripted freestyle dance count as artforms, then I don’t see why sports games shouldn’t.
A lot of people resist classifying sports that way because they think it implies that the outcome is somehow predetermined so the contest is faked. But an art performance doesn’t necessarily have to have a predetermined outcome: it can be, say, an unscripted improv, or a competition whose outcome depends on the decision of judges.
I would have said “ballet”. But then I saw Michael Pink’s haunting Dracula, with John Welker of the Atlanta Ballet in the title role, and was utterly entranced. To this day it’s probably the most amazing live performance of any artform that I’ve ever seen.
Likewise Broadway musicals…until I saw Kinky Boots. And I did grow up listening to the original cast recording of Jesus Christ Superstar. But the rest of musical theater - especially the “classic” Jerome Kern/Oscar Hammerstein/Tin Pan Alley songbook - l wouldn’t mind or even notice its total disappearance.
So for the artform over whose death I would not mourn, I’d have to say: jazz.
Modern day country music.
I respect and enjoy the old timers - Hank, George Jones, Cash, Willie.
But country music could have fallen into a volcano 'round 1970 and I’d be fine with that.
mmm
No, they’re athletic teams trying to achieve the goal of getting the most points, the shortest time or whatever.
If they could find a way within the rules to better attain their goal, they’d be doing it whether you found it artistic or not. People performing art are explicitly trying to evoke some kind of emotional response which is not the goal of the sports team (arguably, it’s the goal of the marketing team). The fact that you find “art” in how they do it is irrelevant and broadens the definition to be meaningless: War is art! Farming is art! Factory assembly lines are art! Perhaps true if you interpret “art” as “skill form” but not as “creative expression” which is the intent of the OP.
Cosplay.
I agree (that sports aren’t art forms, unless you broaden the definition further than I want to). But some Olympic events (e.g. figure skating) are more art than sport.
I’d say they have an artistic component such as working your routine into a whole but I’d argue that they are more sport than art. As I understand them, they’re scored on technical merits and properly spinning, leaping or landing means more than creating a raw emotional response from the viewer. I don’t really follow them though so if there’s a scoring category that’s not based on technical merits, I accept the correction.
I didn’t get that last night, now I do-do.
Poetry
Rap
Steampunk
What? Were you trapped in a box?
Musical movies or in theater.
When they break into song, I literally squirm in discomfort.