Rhythm depends largely upon the elements of pattern and movement to achieve its effects. The parallels between rhythm in sound/ music are very exact to the idea of rhythm in a visual composition. The difference is that the timed "beat" is sensed by the eyes rather than the ears.
Visual rhythm can be created in a number of ways. Linear rhythm refers to the characteristic flow of the individual line. Accomplished artists have a recognizable manner of putting down the lines of their drawings that is a direct result of the characteristic gesture used to make those lines, which, if observed, can be seen to have a rhythm of its own. Linear rhythm is not as dependent on pattern, but is more dependent on timed movement of the viewer's eye.
Repetition involves the use of patterning to achieve timed movement and a visual "beat". This repetition may be a clear repetition of elements in a composition, or it may be a more subtle kind of repetition that can be observed in the underlying structure of the image.
Alternation is a specific instance of patterning in which a sequence of repeating motifs are presented in turn; (short/long; fat/thin; round/square; dark/light).
Gradation employs a series of motifs patterned to relate to one another through a regular progression of steps. This may be a gradation of shape or color. Some shape gradations may in fact create a sequence of events, not unlike a series of images in a comic strip.
Emphasis is also referred to as point of focus, or interruption. It marks the locations in a composition which most strongly draw the viewers attention. Usually there is a primary, or main, point of emphasis, with perhaps secondary emphases in other parts of the composition. The emphasis is usually an interruption in the fundamental pattern or movement of the viewers eye through the composition, or a break in the rhythm.
The artist or designer uses emphasis to call attention to something, or to vary the composition in order to hold the viewers interest by providing visual "surprises."
Emphasis can be achieved in a number of ways. Repetition creates emphasis by calling attention to the repeated element through sheer force of numbers. If a color is repeated across a map, the places where certain colors cluster will attract your attention, in this instance graphing varying rates of mortality from cardiovascular disease.
Contrast achieves emphasis by setting the point of emphasis apart from the rest of its background. Various kinds of contrasts are possible. The use of a neutral background isolates the point of emphasis.
Contrast of color, texture, or shape will call attention to a specific point.
Contrast of size or scale will as well.
Placement in a strategic position will call attention to a particular element of a design.
Prolonged visual involvement through intricacy (contrast of detail) is a more unusual form of emphasis, not as commonly used in Euro-American design, though it is common in many other cultures. In this case, many points of emphasis are created that are to be discovered through close attention to the intricacies of the design.
Unity is the underlying principle that summarizes all of the principles and elements of design. It refers to the coherence of the whole, the sense that all of the parts are working together to achieve a common result; a harmony of all the parts.
Unity can be achieved through the effective and consistent use of any of the elements, but pattern-- that is, underlying structure-- is the most fundamental element for a strong sense of unity. Consistency of form and color are also powerful tools that can pull a composition together.
However, unity also exists in variety. It is not necessary for all of the elements to be identical in form providing they have a common quality of meaning or style. For example, fashions from a specific period share common features of silhouette, materials, and color that identify the style of the day, or the look of a particular designer.
Unity can also be a matter of concept. The elements and principles can be selected to support the intended function of the designed object; the purpose of the object unifies the design.