A harmonious design is created by using similar elements. Harmony in art is achieved when related or compatible visual elements - such as colours from the same family, shapes of similar character, or textures with shared qualities - are combined so that they work together pleasingly without jarring contrasts.
Large shapes alone do not ensure harmony; a composition of large shapes in clashing colours or conflicting styles would lack visual unity. Clashing colours create discord and tension, the opposite of harmony. Conflicting patterns similarly produce visual dissonance rather than a unified, agreeable design.
Exam tip: harmony and unity are closely related principles. Harmony is achieved through similarity and compatibility of elements; unity is the overall sense that all parts belong together.