Finally I found the answer to the question that got me start on this forum.
It's "I Go Crazy" by Paul Davis (1977). The title is prophetic because it was definitely driving me crazy trying to figure out this one. I guess the tune was burned into my little grey cells because the song was on the charts for 40 weeks (a record at the time).
The ringtone is sampled from a short instrumental section of the song which appears about 3:30 minutes into the following video:
YouTube - Paul Davis- I go crazy
I wish I could say I figured it out on my own but the International Trivia Guild would banish me for life iffen I didn't fess up that I had help... win some, lose some...