The second movement of “Pathetique” Sonata is in large ternary form. The formal scheme of the movement is:
A (bar 1-36) —- B (36-50) —- A’ (51-73)
The A section (bar 1-36) is in small ternary form. Part A occurs between bars 1-16. The form of theme (1-8) is hybrid with 3 + 5 phrase structure. Bars 9-16 is the exact repetition of theme, yet the only difference is that melody is placed 1 octave higher. Part B (17-28) is divided into two. Since the Part A is in a major key, we expect that Part B will occur either in dominant (V) or in relative minor key. In this case, both of them are available. It starts as a dominant pedal of f minor (relative minor of A flat major) and then modulates to E flat major (dominant of A flat major). Bars 29-36 is where the Part A repeats itself with the theme and closes the A section of movement.
The B section (bar 36-50) is in A flat minor as it is the contrasting part of the movement. Between bars 37-44, there is a theme which is in sentence form. First 4 bars is presentation and the remaining 4 bars is continuation with an enharmonic modulation to E major. The rest of the B section is looser in terms of form as it prepares the coming A’ section with an enharmonic modulation from E major to A flat major.
The A’ section (bar 51-73) starts with the main theme as expected and its repetition comes again in 1 octave higher (51-65). Bars 66-73 are in the role of coda.