@621Chopsuey
Wait, is Cheerilee still under the Dazzlings’ spell? It says here that the whole school (except the Rainbooms and DJ Pon-3 and possibly Wallflower Blush) were brainwashed by the Dazzlings.

@j4lambert
Well, the whole Battle of the Bands was actually just a fake. That’s because it was a setup by the Dazzlings to get their Equestrian magic back, and turn humanity against each other and become loyal brainwashed slaves by growing more powerful by absorbing the negative emotions of Canterlot High students and possibly the rest of the human world to take over the human world and possibly Equestria in the other dimension and make the HuMane turn against each other so they can feed off their magic and defeat them so easily by shattering their friendship bonds. The Dazzlings are the ones responsible for creating the Battle of the Bands. They were even willing to manipulate Celestia and Luna to let the Rainbooms compete in the finals after performing in mid-performance by letting go into the amphitheater and manipulate Trixie and the Illusions to trap the Rainbooms under the basement of the amphitheater to feed off their negativity and the Magic of Friendship and the magic that Sunset Shimmer brought into the human world to break up the Rainbooms forever and conquered both the human world and possibly Equestria. This would explain that Sunset Shimmer realizes the Dazzlings’ true intentions and is able to stop the arguing by freeing the Rainbooms from being under the Dazzlings’ spell. And after being set free from the Dazzlings’ spell, the last thing the CHS students and faculty remembered that they’re in the cafeteria or in their classrooms and offices until something bad happened to them. This would also explains that all of the brainwashed victims that were set free from the Dazzlings spell discover that they made them become complete jerks. Even Flash Sentry reunite with Twilight Sparkle for real at the end of the film. Also, when Dazzlings lose their powers and pendants to the Rainbooms and the Magic of Friendship is restored, their voices have become a little hoarse. This makes everyone booing and jeering at them in anger for their crimes by turning them against each other. And also, a musical showcase is actually a friendly competition/variety show that is organized by both students and faculty to raise money for after-school programs. This would explained that the Dazzlings turns the variety show into an all-out battle of the bands which is suspended by the Rainbooms after breaking the Dazzlings spell at the end of the film. This would explain that a real Battle of the Bands which is between the Rainbooms and the Dazzlings happens at the climax of the film. Think back at how in Disney Pixar’s Cars 2, the World Grand Prix was a setup by Miles Axelrod, the leader of the Lemons to turn the world against alternative fuels. That’s because Miles Axelrod have created the World Grand Prix and Allinol to make Allinol look bad so everybody go back to using oil and make alternative fuel look bad because Allinol is lethal to race cars.

@j4lambert  
‘Cause she wasn’t competing.

@Zahnrad  
There is some possibility that the winged Diamond is a fashionista group.

One with gems are definately the dazzlings, I think the one you put them as are photo finish, I also assume the one above dazzlings are dramas and the one above that are either diamond dogs or something to do with the crystal empire.

Someone should remake this with the correct identifications.

@OneOverTwo  
Just checked, clef hearts red-gems are in fact the Dazzlings.

I’d really like to see full Derpy, Bulk Biceps, Octavia and CMC performances.

Gotta say, I actually really like some of these emblems… Like the CMC’s Skulls, it’s crazy but I’m not complaining.

@621Chopsuey  
Cheerilee was also unaffected by the spell.

The mane 6 won the battle of the bands due to the disqualification of Trixie for illegal reentry and the disqualification of Adagio for disorderly conduct.

@Mad Black  
Well you get a brief taste of what Derpy’s band sounds like.

The one with the theatre masks are almost definitely the Drama kids.
 
& the Dazzlings are probably the one with the red gems with a G clef & hearts all over the background.

Ohh I wish we saw more of the performances. Especially Derpy, CMC, Octavia, Bulk Bicepts, Lyra & Bon Bon. I kinda wish they would put that on DVD…  
But no, we got Snips and Snails for a stupid bad music joke…

Who the heck got the Dazzlings confused with the Snapshots?

@621Chopsuey  
No, I agree - the only slim reason is the musical note mark being hers, a consistent theme for most of the other BG human groups.
 
But I’d rather say we were looking at the nerd clique, doing something like out of the end of Revenge of the Nerds-type musical show.

@Masem  
I don’t believe Vinyl participated. Like Spike said, she was unaffected by the Dazzling’s spell because she’s always wearing her headphones.

@Tesou  
The drama club is Tumblr.

Top left we’ve come to determine to be Thunderbass’s group (with his CM front and center on the logo)  

 
The second right one I’m split between DT/SS or the Diamond Dogs
 
The one below that is the drama clique group
 
The one on the left with the note and record is very likely the nerd clique but could be DJ PON-3 (though we have no evidence she even participated.

Top Left are the Rocker Group.  
The green one are the techies.

The one in the top right is the Snapshots. (Photo Finish’s band)  
Below that is the Diamond Dogs.

@soundtea  
agreed.

No, that red gem one on the right with the 3 music notes is the Dazzlings. The shutter one is Photo Finish’s group with Pixel Pizazz and that other girl.