I'm betting that the harmonies and chords you have stuck in your mind are probably those of the Lettermen. They had a way of doing that kind of thing with most of their songs, such as, "When I Fall In Love (it will be forever)". Gosh, I wonder how many parties I attended that played Lettermen and Mathis albums in the later hours...

Of course, while nearly everyone else was in the corners making out or else dancing real close, I was in the next room singing and playing folk music with the other dateless people there.