I too have been searching for this intro.😂 I feel like it may be a show my mother watched, as I was born in '79, and it reminds me of the intro to a more adult-targeted show.
Now, I don't think I've found what I'm looking for, but I may have found what some of you seek. It is an '80's show with a nearly identical into to the Chicago song. It is only the first riff(approx 6-7 sec), but it is as close as I've come. Now I sometimes watched this show as a kid, but I still think I'm looking for a different intro...even though it is also that beginning 6-7 sec riff of the Chicago song that I remember as a tv show intro from my childhood. When I heard this intro I just found, I could hear the similarity to the Chicago song(listen to them back to back and you'll see)...but it isn't the exact sound I remember. Hopefully this is what some of you were looking for though:
Eight is Enough intro:
https://m.youtube.com/watch?v=Brn74NyozsM
Please listen specifically to the first 6-7 sec of the first version in the link, because there are other versions that are different that you may come across if you just do a search.
Ok, back to my never ending search. My memory of my childhood is abnormally accurate, but if I exhaust every show from the '50's(Nickelodeon reruns) through the early '90's and I still don't find it, I may have to accept that it IS the Eight is Enough intro that I am remembering, and my brain just incorrectly remembered the mystery intro as being slightly different than it actually is(closer to Chicago's version). If this happens, then I'm going to have serious trust issues with my brain.😒 🙄
All the best to everyone hunting down memories.🙏