I always thought it was amazing how well the personality of every aeon was captured in the hymn. Listening to them...

Valefor's is soft and pretty, maybe gentle. Fitting for Valefor
Ifrit's is strong, deep, pure power.
Ixion's sounds older, perhaps wiser. For some reason, I got that feeling off of Ixion.
Shiva's is beautiful, but not gentle like Valefor's was. It's fitting for the vision of beauty that Shiva is
Bahamut's is sung by a child, which I always found strange because it's the strongest of the 5 main aeons. Maybe it's to show the potential within children, that they have the strongest spirit, I don't know.
Yojimbo's is strong and noble, fitting for a samurai, for sure.
Anima's is sorrowful, maybe haunting. It shows the deep pain that Seymour's mother felt.
The Final Aeon's is haunting, eerie, and just unsettling when compared to the rest, showing the darkness surrounding what the final aeon is.