Harmony isn't considered a threat to infinity unless they are very skillful (like this guy in the video), because most of the skills, including their acupuncture skill - which is set to be a "Grab" skill, are counter-attackable. Harmonies, however, will look for opportunities to acupuncture you when you cancel your Moonfire by pressing "X", or the instant that you jump or fall to the ground, so just watch out. Their combo hurts a lot when they successfully acupuncture you.