Thanks, A.J.
I found it at Wikipedia:
"If You Don't Know Me By Now,"
produced & written by Kenny Gamble
& Leon Huff, and 1st performed in 1972,
by Harold Melvin & The Blue Notes.
It was originally written for Patty
LaBelle's group, LaBelle, but wasn't
recorded by LaBelle until later.
In the USA, it topped the USA- R & B
(Rhythm & Blues) charts, and was #3
on the USA Billboard charts.
The RIAA (?) listed it as "one of the
"Songs of the Century".
These "ghost songs", sometimes
called "mystery songs", are often
stored in my transient brain, and
seem to "pop-up" in my musical
memories, sung in my head.
Your naming of the song title gave
me a clue, a reference to the song's
identity.
Best Regards, Stay Healthy
John Broecker
The Milwaukee Mesopotamian
(I wrote The Epic of Gilgamesh)