harmony

noun6

1. •
   A pleasing combination of elements, or arrangement of sounds.
2. •
   a calm state of agreement between people or groups, with no fighting among them

   • December 4 2010, Evan Thomas, "Why It’s Time to Worry", in Newsweek America's social harmony has depended at least to some degree on economic growth. It is easier to get along when everyone, more or less, is getting ahead.
3. •
   Two or more notes played simultaneously to produce a chord.
4. •
   The relationship between two distinct musical pitches (musical pitches being frequencies of vibration which produce audible sound) played simultaneously.

   • I did not know anything more about music,only about finger exercises, difficult tasks, contradictions in the theory of harmony, and tedious piano lessons from a sarcastic teacher who saw in my […] — 2012
5. •
   The academic study of chords.
6. •
   A literary work which brings together or arranges systematically parallel passages of historians respecting the same events, and shows their agreement or consistency.