rock song from the 60's or 70's-Help please!! Thank u

Hello there to the forum users!
I am trying to help my husband identify/locate a song he believes is from
somewhere in the late 60's or early 70's (could be earlier)

The only things he knows are these:
rock
black singer (american?)
phrase: SLOOPY HANG ON (or..mm..maybe "come on sloopy")??!) is in the text
Long song-around 20 minutes!!

That's it, I would really appreciate if someone has a clue to this
Many thanks and Have a great weekend

it is called "Hang on Sloopy" by The McCoyys. was in the 60's. But its not 20 min long though, the versions I find are around 4 min long. hope this helps.

I had also managed to find that song, and even found a sample of it on amazon, by a group called the yardbiords ('64 in UK) but hubby laughed when I played it to him..
he insists there was a black guy and it was a 20 minute song with those words in it.. I can't find a thing in my searches..
Thanks anyway!!