Activating Harmonics requires the fulfillment of two conditions, and successful execution will allow Battle Members to perform their actions consecutively. The activation conditions are the turn order of participating Battle Members must be consecutive, and Takt still has Action points remaining.
Once activated, a minimum of two people and a maximum of five people can take action at once. Because of the increased number of consecutive hits, it becomes easier to earn Combo Bonuses.
Additionally, by using particular Skills one after the other during Harmonics, the ultra-powerful Chain Skill attack will be activated and usable. Obtaining an Expansion Disc will allow the use of Chain Skills. By performing particular Skills in a particular order during Harmonics, Chain Skills will activate.
When activating a Chain Skill, moves must be consecutive and each Skill must be performed by different battle members. If the same member uses multiple Skills, the activation disappears.
The conditions are complex, but Chain Skills are stronger than normal Skills. Also, when Chain Skills are used on an enemy in Field Break status, Pursuit will occur. It deals more damage than normal.
The Expansion Disc item that allows the activation of Chain Skills can be received as a Quest reward. Also, sometimes Expansion Discs will be lying out on the field as a Lost Item.
Another point of caution: Once Harmonics is selected, Support Commands become unusable, and once activated, Harmonics cannot be canceled.
Acquired Chain Skills can be viewed under Chain Skill from the Skill Menu.