noun
plural -nies
the combination of different musical notes played or sung at the same time to produce a pleasing sound [noncount]
[singular] :a pleasing combination or arrangement of different things
When things are in harmony or when one thing is in harmony with something else, they go together well or they agree with each other very well.
When people are in harmony or in harmony with each other, they live together in a peaceful and friendly way.
To bring something into harmony with something else is to change it so that it agrees with or matches something else.
When things are out of harmony or when one thing is out of harmony with something else, they do not agree or combine well.