Some music teacher on TV (I think, it was years ago that I saw this) said she could teach anyone to sing at least fairly well.
She said anyone can sing, any voice can be trained. Is she right? What about tone-deaf people?
I'm not a singer, but I haven't yet met anyone who I couldn't teach to at least get a tune out of their instrument. Normally, even the worst-sounding playing is due to at most 3 issues of technique.
Never had someone who was actually tone-deaf; most people who think they are aren't.