For example, it is normative for the secondary theme of a minor-mode sonata to be in either the key of III or v. If a composer chooses to break this norm in a given piece, that is a deviation that requires analytical and interpretive explanation.
"[4] A work in sonata form is expected to accomplish certain goals; how it goes about this task is to be understood in relation to a set of background stylistic tendencies.
The theory, then, understands the sonata as an example of dialogic form: the compositional choices that create an individual piece of music are in dialogue with generic norms and expectations.
At any point in a sonata movement, such as at the beginning of the secondary theme or the end of the development, a composer had various choices for how to proceed.
"[7] A central part of the analytic and interpretive work of Sonata Theory lies in recognizing these deformations and default choices and understanding how they affect the progress of a piece as a whole.
From the perspective of the theory, sonata form engages two principal levels of compositional design: tonal and rhetorical.
The rhetorical form, on the other hand, concerns the manner in which themes, textures, and musical ideas are presented; it "includes personalized factors of design and ad hoc expression: modular and textural layout, selection and arrangement of musical topics, varieties of structural punctuation, and so on.
Later sections of the piece (such as the development, recapitulation, and coda) usually revisit these ideas in the same order—though not necessarily touching on every one—as if rotating through a pre-set sequence, like hours on a clock or channels on a television dial.
One function of this space is to define the main (or tonic) key of the piece, usually confirming it with a cadence at the end of the theme.
The most common goal for the transition's energy gain is to drive to the first moment of "structural punctuation," the medial caesura.
Often, and with increasing frequency in the nineteenth century, (but by no means exclusively) the secondary theme is marked by a quieter, more lyrical character than the energetic TR that preceded it.
(One common manner in which this is accomplished is the articulation of an apparent second medial caesura, producing what Sonata Theory terms a Trimodular Block.)
Thus the EEC is conventionally defined as "the first satisfactory perfect authentic cadence that proceeds onward to differing material.
The entire sonata form, therefore, is understood as a dynamic trajectory toward the ESC, the basic plan of which is foreshadowed by the exposition's approach to the EEC.
The crux is the part of the recapitulation where the S zone secures itself in the home key and significant changes compared to the exposition no longer occur.
Thus it often happens that the restoration of the tonic key in Rotation 2 is accomplished by the arrival of S. This has led other analysts to apply the term "reversed recapitulation" to this sonata type.
Sonata Theory, in contrast, reserves the term "recapitulation" for instances in which the beginning of a rotation coincides with the return of the tonic key.