Was there actually a Derek in Derek and the Dominos?
Outside my musical orbit I’m afraid. 
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Captain Beefheart
Jo Jo Gunne
Dr Feelgood
Rufus
I’ve heard that Marilyn Manson the person gets visibly twitchy when people refer to him as Brian Warner nowadays.
I used to think that Sting was a band.
The stage name of their singer/songwriter. Doesn’t qualify, not even in the “Alice Cooper” sense, since the band was originally “Captain Beefheart and his Magic Band.”
He’s still a real person, the frontman of the band in question, if not “the” actual lead singer.
Overheard while standing in line at the LA Forum back in the day. For a Tull concert, of course.
Mason Proffit was a fairly obscure country-rock band, but not a person.
Speaking of the fairly obscure, and with Captain Beefheart justifiably disqualified, I’m going for a promotion with Brigadier Ambrose.
Hatfield and the North (who, I think, got their name from a highway sign north of London).
Me, a while ago: So you are saying that the singer from Belle & Sebastian is actually named Stuart? Not Sebastian? That doesn’t make sense! Now you will tell me that the chick is not Belle.
Brian Jonestown Massacre
Commander Cody and the Lost Planet Airmen
Echo and the Bunnymen
Vince Vance and the Valiants
You probably know this already, but Belle & Sebastian is the English name of a kid’s book & TV show from France called Belle et Sébastien.
“Commander Cody” is the stage name of the lead singer. Doesn’t fit.
However, Cat Mother and the All Night Newsboys had no one named “Cat Mother” in the group.
“Echo” was the drum machine they used before they had a real drummer (the late Pete de Freitas).