In the early big band days, union sanctioned contracts read ’14 (or whatever number) musicians and a drummer’. That certainly would not be applicable today at least for big band and show band drummers – did you ever see a big band or show band drum chart?
The voice is recognized as a musical instrument that can be developed and improved, and that can and should be trained as much as any other musical instrument.
IMHO, Me-thinks that the person who posed the initial question is merely a provocateur and is really not seriously concerned about whether or not a vocalist is a musician.
Gary, I do Flip Flop and Fly just about every gig … I’ve been using a midi file for the past several years that is much hipper than any styles I have.
Ciao,
Jerry