How did Franz Liszt’s Piano Sonata in B Minor depart from the usual Classical sonata structure?

Franz Liszt’s Piano Sonata in B Minor (1853) departs from the traditional Classical sonata structure in several key ways:

• Single-Movement Design: Unlike the typical Classical sonata, which consists of multiple distinct movements, Liszt’s work is composed as a single, extended movement. This movement contains internal subdivisions that are analogous to the sections of traditional sonata form but are integrated into one continuous whole.1
• Thematic Transformation: Rather than relying on the Classical principle of contrasting themes and keys, the sonata is built upon four themes that are transformed and combined in a free, flexible manner. This method of "transformation of themes" allows a few musical ideas to provide the basis for the entire composition.21
• Departure from Abstract Form: While the Classical sonata is defined by the exposition, development, and recapitulation of thematic material based on key contrast, conflict, and reconciliation, Liszt’s approach prioritizes thematic unity and fluid development over these rigid formal requirements.1