What is the significance of the robe, and the annual Song to the social stability of this society?
In Gathering Blue both the robe and the Song are methods by which the Council keeps control of society. Gathering Blue is a "companion" book of The Giver; both are set in the future after an unspecified disaster has changed the world. In Kira's society, the Council is all-powerful. Like many powerful organizations, a lot of their energy is spent on keeping that power. In Gathering Blue strict control is kept over the people's knowledge of the past. Kira's job is to add to the robe, which is a visual story of the society's past. Emphasis is on angry, hot colors such as orange and red. Blue is too peaceful for the Council's purposes, but Kira works to insert them. The Song is added to every year and is sung once per year. It serves the same purpose as the robe but in words. In general, the Council benefits from encouraging a view that death and destruction are inevitable, and that trusting in the Council is in everyone's best interests. Although you do not ask about it, there is a third symbol of the Council's control, which is the staff. It is also added to every year with new carvings, and is held by the singer of the Song, while wearing the robe.