adjective
harmonic
har-MAH-nik/hɑːrˈmɑːnɪk/
Relating to the combination of musical notes into harmony.
The pianist creates a harmonic combination by sounding three notes together.

Etymology
Harmonia literally meant a “means of joining,” including the joining of ship-planks, and also meant concord of sounds. Harmonic describes musical tones that fit together pleasingly.
In context
western music where close intervals are thought of as dissonant and harmonic intervals like the fifth are considered consonant
More examples
- She analyzed the song's harmonic structure.
- The composer introduced an unexpected harmonic change.
- The voices formed a pleasing harmonic combination.
Forms
harmonic
harmony noun — the combination of musical notes