Forged by the Golden Melody Weapon Guide

Every 10s, the equipping character plays a "Harmonic Movement" of the corresponding type for a boost in the following order: +18% ATK > +120 Elemental Mastery > +28% Stellar Glimmer reaction DMG. Each instance of Harmonic Movement lasts 10s. This effect can trigger even when the equipping character is not on the field.
Triggering a Stellar Glimmer reaction will also grant an additional 12-second instance of "Harmonic Movement: Contrapuntal" with the same effects as the Harmonic Movement active when Stellar Glimmer is triggered. This effect stacks with the original Harmonic Movement effect, and can trigger once every 12s.