Harmony is the peacemaker: someone who gets people to come together and helps show everyone that they are all on the same team, even if they don't all play the same position. The Harmony personality does not have to be right. Rather than win for the sake of winning, this is the person who is willing to compromise, as long as the bottom line meets everyone's needs and expectations. Contrast that with the bullheaded, argumentative type, and then decide who is more likely to move a project forward.
This is the diplomat: someone who is tactful and sensitive. By carefully steering conversations away from passionate disagreement, this person will be able to keep warring sides at the negotiating table a little longer; perhaps long enough to work out a treaty or a solution.
This is the arbitrator: the judge who can hear both sides of an argument and point out the areas where people are already in agreement. With the right tools and support, they are the key to progress and win-win negotiations. They are unlikely to back down on their own values, but they are willing to concede that someone else might know as much as they do, and they will seek information over ego.
Others might be louder, more passionate or more forceful, but someone whose strength is Harmony is not a pushover. He or she just prefers not to argue. He or she might walk away when a co-worker is shouting to make a point. But the world, and most organizations, need both kinds.