I recall there being a word for nasal singing, I might be imagining things, but haven't had any luck finding that word on Google. Does any one have any suggestions?
How about the term "rhinophonia?"
Are you talking about nasal voices? If you are I have some medical jargon for you.
rhinolalia is the medical term for this nasal speech. This can be further classified into hyponasal speech (hypo-rhinolalia) and hypernasal speech (hyper-rhinolalia). Wikipedia has a superficial discussion on these topics if you care.
Hope this is helpful.