Harmonic Resonance is an origin trait in Destiny 2 that can appear on 1 weapon. There is also an enhanced version with a stronger effect.
What Harmonic Resonance does
Equipping multiple weapons from this set grants this weapon increased reload speed and handling. It also deals increased damage versus targets wielding Light and Darkness.
Enhanced version
Equipping multiple weapons from this set grants this weapon improved reload speed and handling. It also deals increased damage versus targets wielding Light and Darkness.