Pete's ass zipper

you wanna see me overthink the beautiful artwork Shiro Amano drew for the 2013 Kingdom Hearts symphony concert? I'll do it!

Xemnas is the conductor cos he da boss

Axel has a flute because maybe it suits his youthful, playful, kind of immature energy? Fairy dust works on him somehow, even tho he's an adult. Do people read into that? Do we talk about that?

Saïx plays the clarinet because he is the Squidward of Kingdom Hearts. He hates fun and he tries to quash his yearnings by being a big meanie pants to everybody instead of facing his feelings like a big boy

Xaldin and Lexeaus play big drums because their magical elements are Wind and Earth, respectively. Wind and earthquakes are loud.

Demyx has a double bass because it resembles his signature sitar

Luxord has a trumpet because trumpets are cool and sexy. He is the gentleman of this organisation.

Xigbar has a saxophone because his swag is more roguish, more shady than Luxord's. If I'm at a cafe with Xigbar and I go to the bathroom I am taking my bag with me

Roxas and Xion share a big marimba together because it's mad cute- but they really share an instrument to reflect the fact that they share a weapon, the Kingdom Key.

Marluxia has a trombone because I guess a trombone is like a scythe if I really want to think of it that way

Zexion has a violin because he's a little nerd. I admit I don't have a strong read on Zexion yet. Someone, put a better reading in the comments

Larxene has hand bells (I think that's what they are, altho they're hard to see) so she can replicate her signature throwing knives pose

And finally, Vexen has a harp because? maybe he wanted to be elegant and precise for a change. Maybe in his head, he's always elegant and precise. Or maybe a harp has lots and lots of strings, just like KH has too many replicas. But now I'm reaching.