The symmetry of form
The fundamental type of the global symmetry of a musical piece is the symmetry of its form 1. In conducting a symmetry analysis of form we will discuss three different planes: the thematic plane, the tonal plane and the structural plane. By the term thematic plane we understand the occurrence of the same or different themes and the work associated with them, by tonal plan we mean the tonal and modulation aspect, and the structural plane implies the thematic and tonal properties expressed by the introduction of metrics, in accordance with the number of measures.
The basic aspects of the symmetry of form are:
We will analyze each of the mentioned types of symmetry in more detail by giving examples of their occurrence within corresponding musical forms.
1"Musical form is an expression denoting the formation of any musical content in such a way that each of its parts is in a state of musical suspense in relationship to the whole. Such a relationship of the parts to the whole, which is necessary, builds musical architecture and texture in which the elements of melody, harmony, and rhythm occupy their correct place. The parts of form may be united in a variety of ways which results in symmetry or asymmetry, development or simple continuation, contrast or analogy, repetition, variation, organic unity or contradiction. Content without form is amorphous and the absence of balance between content and form leads to non-proportionality, whereas hypertrophy of form produces an empty scheme or boundless complexity." (Lemacher and Schroeder, 1967, p. 5).