>(And why our obsession with new-ness as some criteria for
>brilliance and greatness? That is another post.)

Yes!

>This isn't without precedent. I think we think of Prince when
>we hear D's dense vocal layers and he does a bit of this vocal
>inversion but it was never a hallmark for him, almost more
>incidental (think of the vocals on the closing refrain of
>"Condition of the Heart"). Riot/Fresh-era Sly is closer imo
>(think the vocals on Just Like a Baby); a lot of p-funk vocals
>too.

Agreed. Great great breakdown.
I honestly think of Marvin and how he harmonizes with himself.
But you're right, the dirty-ness of voodoo/black messiah reach back to
'Riot','Cosmic Slop' and 'Standing On The Verge'.
(I need to go back and re-listen to Condition Of The Heart with this new context).

BUT, I'm SO glad you brought this up because it leads to a point I was going to make in my reply above.
And before I say it, I want to acknowledge it was OKP HotThyng76/SoWhat that originally brought
this to my attention in a post in The Lesson YEARS ago.
And it really opened my eyes to the polarization with not just BS/Voodoo, but D'Angelo the artist.
So HT76 deserves the credit for this but:

Voodoo is one large inside joke.

I have an iTunes playlist that includes songs that were sampled by and influenced Voodoo. The first song is 'Four' by Madhouse/Prince.
If you've listened to almost ANY of the QLS podcast you've heard Quest tell the story of how he charmed D'Angelo at a Roots show playing
the drum part of this song (he tells the story like every other episode). These two dudes are huge liner note music nerds.
The Voodoo sessions are filled with them just messing around playing Sly, Funkadelic, Johnny Guitar Watson, Stevie, Prince, Ohio Players, etc.

They wanted you to listen to Voodoo and hear their favorites.
It's a love letter from D & Quest to fans that love those funk bands.
'Greatdayinthemornin'' is groove for groove sake.
In fact, outside of Left & Right, all the songs are over 5 minutes.
That's groove.

So your explanation of his vocal style above is EXACTLY what fits with this groove they were making.

Again, Voodoo is one large inside joke.