i think CD has a deeper, maybe slightly raspy voice. mud sounds like mud bird has a fruity, silly accent (like the swedish chef, though i know he's not a swede) and medium pitched voice.
I picture Tree-Hugger as having a southern accent, but speaking at a faster pace for a southerner. I've heard KC and Daisy and Sam and Vixen and Mera, so I picture their voices. For Seamonster, I picture a slightly deep voice with a humorous tinge, as if he smiles through his voice. HHB sounds like Cooter in my mind. HCM has no accent at all. Standard Americana. WHC has a sexy smokey voice in my mind which is contradicted with a Bob & Doug McKenzie accent. Hotwater sounds exactly like Wayne Brady. Luckystripe sounds like she's from Boston with a slightly nasal voice. Antithesis sounds Canadian in my mind for some reason.
I only do that when I'm reading things that my friends have written or something... So, basically, I can only do that when I already know the person's voice.