1. Modulation: The bridge typically modulates from the tonic key of the exposition to the dominant key or another closely related key. This change in key creates a sense of harmonic movement and tension.
2. Connection: The bridge connects the exposition and the development section. It provides a smooth transition between the two sections by linking their musical material and thematic elements.
3. Development of Motives: The bridge often develops and transforms motives or themes from the exposition. This development process creates a sense of continuity and helps maintain the integrity of the entire sonata-allegro form.
4. Contrast: The bridge provides contrast to the preceding exposition by introducing new thematic elements or changing the texture, dynamics, or rhythm. This contrast adds interest and variety to the sonata-allegro form.
5. Building Tension: The bridge can build tension towards the development section by intensifying the harmonic progression, increasing the dynamic levels, or introducing dissonant harmonies. This creates a sense of anticipation and leads into the more elaborate and contrasting development section.
Overall, the bridge in sonata-allegro form plays a crucial role in connecting the exposition and the development, modulating between keys, developing thematic material, providing contrast, and building tension.