The word harmony originates in a pair of old Greek words - one a noun that defines a joint agreement, the other a verb that means to fit or join together.
Normally, when we think of harmony, we think of the way music sounds - of contrasted notes and vertical progressions - one higher, one lower - blending together to create a single element of beautiful sound. The melodies may be different, but the music that the contrasting notes follow along their separate paths fits together in a perfect way.
I can think of no better way to describe my parents relationship. They are very different people, my mom and my dad, but they complement one another in a way that fits together in a beautiful example of what a marriage should be.
The church my parents attend updates the church photo directory every couple of years. This year was an update year, so I have this wonderful photo. They'll celebrate their 57th anniversary this year.
Mom, Dad, this one is for you. I love you both!