This site introduces unknown Emanuel Bach (C. P. E. Bach).
ChatGPT4o writes as follows (please note that it may not be accurate):
Emanuel Bachʼs Fantasia in F Major Wq. 59-05 (H. 279) is one of the works that showcases his original style. This piece is characterized by its free form and improvisational elements, featuring unpredictable developments that surprise the listener. From the outset, it employs rich harmonies and bold modulations, drawing the audience in. In this work, Bach expresses a wide range of emotions, skillfully combining contrasting sections. Performers are required to have advanced technical skills and expressiveness, allowing for new interpretations with each performance. This fantasia demonstrates the innovation in 18th-century music and influenced later composers.