Thanks for the tips. Alternator belt is new and tight. Battery is fully charged. I'll check the starter motor bolts, but the "howl" seems to happen after the starter has "done it's thing" and is completely out of the picture, so to speak.
Odd noise for sure. I've never heard anything quite like this noise.
My worst fear is that it involves the vacuum pump. Although, that unit pulled a nice steady 20psi on the gauge when I checked it.