999's bright idea of browsing online (funny that I didn't even think of poking around the internet to see if I could learn something about it!) has sent me browsing online..and it looks like wiki is saying the same thing as both reputable-seeming and junk-like sites.
You're apparently either born with it or it follows head trauma.

The ENT I'll be seeing was chosen by the nurse who set up the appt for me. She said he will scope my throat during my initial appointment if he thinks it needs done..which kind of creeps me out, but it's a relief to my poor broken glottal flap thingy.
Maybe he'll be set up to do tone deaf testing.

It seems odd that my music-memory still works. My timing is still good and I can fake well enough to seem like I'm still musical. That's a pretty weird thing to fake!

I can still hear whether tones match or are higher/lower.
I played with a group last weekend and couldn't hear whether I was matching everyone else..I relied on my eye and memory instead of my ear and instinct.

Here's an online test I ran across (and did not do..I don't have a headset)
are you tonedeaf too?