It's a two-pronged thing; being both sensitive to the Void and good with music. And Biomancer clearly can't replicate mental powers; he had to do a mind transfer to replicate Unity. (And the flavor text on the Carbon Adept states that the fleshchild is "out of tune".)
Your explanation makes sense, though, even if it raises more questions. (Also now that I think about it, this all goes a fair way towards explaining why Golem Unity has to cast her bots from hit points.)
I just like Biomancer; he's fascinatingly creepy. (I can just imagine Christopher & Adam's "Egad, what is wrong with you?" reactions now.)
Oh yeah, Biomancer is going to be a fun episode, I also love the idea that, really, Biomancer rarely interacts with the rest of the world. He's just in his lab, being creepy and doing experiments and then occasionally he heads to the surface for a thing or two and causes a massive ruckus whenever he does.
Biomancer is also one of the very few long-lived characters who has any inclination to stick his (creepy) nose into superhuman things, so lots of potential there. We may even find out the secrets behind why Biomancer is teaching us about shapes. ;3
My guess is that his symbology on his clothing is one of the 4 elements charts. I've seen a lot of different versions that delineate Earth, Air, Fire and Water and his looks vaguely familiar with at least a few of those symbols, plus he probably has an Alchemy background considering his nemesis the Scholar.
But, that's just a shot in the dark. Could be a lot of different things
>_>;; I know it's probably classical elements symbology (reminds me of what was used in The Fifth Element for instance)... I was echoing the running gag the Twitch folks make whenever Biomancer shows up.
(I reiterate my lament of needing to learn how to make my jokes more obvious...)