Ivie was beyond category.
Ozzie Bailey, yeah! Tony Watkins too.
Other than Ivie, Ellington's vocalists, the male ones in particular, seem to have been less than universally loved in their time. There's been at best a partial market correction since. But jeez, they were pretty much always there in some form or fashion, so what does that say about Duke? Pretty much that that "thing" was a part of his palette and damned if he wasn't going to use it.
You can't see the whole picture unless you see every color, texture, shape, etc/whatever. And with Duke, there's no end to how much of that there is, from beginning to end. I entertain no illusions that I'll ever be able to see the entire picture all at once, other than the people who were there all the way, and ultimately, that's Duke and nobody else. It was his to create, it's ours to discover, and unless/until proven otherwise, it's as close to infinite as there is.
Now, having said all that - Money Johnson, hmmmm....