Discuss how repetition and contrast create structure in music. Include descriptions of several fundamental musical forms.
To answer the question directly and succinctly, repetition and form in music create predictability in two different ways. Repetition creates predictability in the sense of anticipation and familiarization. When someone hears something repeated, it gives them a level of comfort that is simply human nature. This comfort causes anticipation, which allows the listener to identify with the music.
Contrast also creates predictability by giving the listener variety and causing the listener to recall the thematic material that is being contrasted, which causes anticipation of the thematic material.
Repetition and contrast are not limited to thematic material. They can also manifest in dynamics, texture and timbre and be used in the same way as described above. All of these elements combined cause structure in music: form, dynamics, texture and timbre.
In the analogy of a building: formal structure (form) is the foundation; texture could be considered the walls and other internal structures and timbre, dynamics and all of the other details involved in music could be considered the decorations and the details that make the music interesting.
In terms of ...
Repetition and contrast are discussed in terms of how they give structure to music by creating predictability. The mention of form cannot be excluded, as form, in its very nature, contains repetition and contrast, thus giving music structure in and of itself. Formal structure is also defined in detail, with references describing the nature, history and common use of the particular forms discussed.