Which musical form was developed during the Classical period?

The multi-movement sonata or sonatina form emerged prominently during the Classical period, aligning closely with the stylistic developments and compositional techniques of composers such as Haydn, Mozart, and Beethoven. This form typically consists of several distinct movements, each with its own character and tempo, which is a hallmark of Classical music's emphasis on clarity, balance, and structure.

During this time, the sonata form became a foundational element for instrumental works, allowing composers to develop themes and explore musical ideas in a cohesive manner. The structure usually includes an exposition, development, and recapitulation, providing a framework for thematic development and contrast.

While rondo form, fugue, and variations each have their origins and significance, they do not exclusively define the Classical period to the same extent. The multi-movement sonata played a pivotal role in the advancement of instrumental music and its formal development, making it a quintessential representation of the Classical era's innovations.