Sonata

 A performer at the circus, he plays the xylophone on his belly--sometimes as its own act, but usually just to accompany/underscore other performers

 Shy and soft-spoken; despite his height and overall size, he's kind of a big baby

 Resting Melancholy Face, but his soft smiles make up for it

 Sound sensitive; he actually wears earplugs when he performs, and most of the time in general when he's in loud places like the circus

 His mane is incredibly soft and fluffy

 Has a firm enough moral code and set of standards, but he's not that difficult to sway into going against them

 Loves music of pretty much all kinds, and can often be caught humming melodies to himself

 Fidgets by tapping his xylophone with his fingers; it makes a soft little ding when he does