Turns out it was REO's first Number One ... and it was also its first real power ballad. Singer/songwriter Kevin Cronin, he of the weenie-ish voice, explained the genesis of the song, and the importance of it to REO's career, in his curiously affecting liner notes to a 1999 REO collection The Ballads:

We considered "You Can Tune A Piano, But You Can't Tuna Fish" an artistic triumph. [ed. Stop snickering] I firmly believed that our musical direction on "Tuna" was the way to go. And although the album went gold, and "Roll With The Changes" became our first Top 40 single, it fell short of our extremely high expectations. I was confused and a bit disheartened, and it showed in my songwriting output for the "Nine Lives" album. Gary wrote "Only The Strong Survive" and Bruce added "Back On The Road", but I came up creatively empty handed. The momentum we had begun with the live album came to a screeching halt, until one day in March of 1980 ...

With our constant touring and recording studio schedule came the problems one might expect on the home front .. we were getting more nuts and the band wives and girlfriends were getting more and more pissed off. There were affairs going on left and right, and numerous numbing agents were at work in all of our blood streams. It was a crazy time, but out of this craziness, some interesting songs began to emerge. Oh yeah, the infamous day ...

I woke up at 4:00 AM, found my way into my studio, sat down at the piano, and listening as the verses to what would become our first number one song kind of wrote themselves. At band rehearsal later that day I sat at the piano again, came up with the title "Keep On Loving You" and finished the song on the spot. The guys weren't sure what I was up to with this "slow song", but deep down I think there was a feeling that we were on to something special. It didn't take long before Gary cranked up his Les Paul, Neal went instinctively to his Hammond organ, Bruce and Alan found a strong rhythm groove, and together we fell upon what would become known as the "REO power ballad."