Form is the quality in a work of art that presents to the mind of viewer/listener an impression of conscious choice and arrangement (design). Form represents order and clarity in art. Form shows itself in the selection of certain details and the rejection of others. Form also manifests itself as it relates to the whole. Much is to be gained by viewing/listening to a work of art as a whole, or unity.

Our daily experiences are composed of sameness and differentness. Certain details are repeated to us over and over. Other details are exposed to us as being new. Music mirrors this duality. The basic law of music is repetition and contrast; or, in other words, unity and variety. Repetition serves to fix the material in our minds while tending to our basic need for the familiar. Contrast sustains our interest but feeds our basic love of change. The interaction of the familiar and the new, the repeated elements and the contrasting ones, will result in the linear nature of musical form.

One other principle of form that comes between repetition and contrast is variation. This occurs when some aspects of the music are altered but still recognizable. We hear this principle in every type of music, from a rap song to the symphony. A cover song of a popular song is also a good example of variation – the tune is recognizable but the known version has changed. The principle of form is embodied in a variety of musical structures. No matter how diverse, these musical structures are based in one way or another on repetition and contrast.