This site introduces unknown Emanuel Bach (C. P. E. Bach).
ChatGPT4o writes as follows (please note that it may not be accurate):
The sonata in the 18th century symbolizes the transitional period from the Baroque to the Classical era in music history, undergoing significant transformation through the development of form and style. During this time, sonatas were composed for various instruments, including keyboard, string, and wind instruments. Solo sonatas and chamber music sonatas, in particular, became widespread.
Early 18th-century sonatas inherited the traditions of the Baroque period, represented by composers such as Corelli and Vivaldi. Their Sonata da chiesa (church sonata) and Sonata da camera (chamber sonata) laid the foundation for the sonata in terms of form and purpose. These works typically consisted of multiple movements and commonly employed binary form.
Carl Philipp Emanuel Bach and Johann Christian Bach pursued rich emotional expression through the Empfindsamer Stil (Sensitive Style), contributing to the development of the sonata form. Particularly, C.P.E. Bachʼs keyboard sonatas are characterized by their free and improvisatory structures, dramatic modulations, and intense emotional expression.
In the late 18th century, composers such as Haydn, Mozart, and Beethoven emerged and solidified the modern "sonata form." This form is structured into three sections: the exposition, development, and recapitulation, emphasizing the contrast and development of themes. Haydn laid the structural foundation, Mozart combined lyrical beauty with polyphonic treatment, and Beethoven introduced dramatic expression.
The 18th-century sonata, with its formal freedom and diverse expression, had a profound impact on the musical developments of the 19th century and beyond. Along with advancements in instrumental technology and increased performance opportunities, the sonata became a central genre for both composers and performers. This eraʼs sonata symbolizes the musical transition where Baroque tradition and Classical innovation merged.