Here's the version that is most memorable. Performed by Johnny Mathis and Deniece Williams.
The song itself is by Jeff Barry and Tom Scott, both very successful songwriters back in the day. It's a great song, and it must be one of the best TV theme songs of all time.
The interesting thing to me is that I've always thought that it was Nick Ashford and Valerie Simpson, and written by them too. I don't know where I got that idea, but it stuck. I've given them credit for it for over thirty years. I've probably posted it here and given them credit. Mea culpa.
This whole library-at-your-fingertips thing is interesting. You can live with your old misapprehensions, or not. It's up to you. But be careful, don't always trust what you find. Professor Google can be wrong too, sometimes!