This site introduces unknown composer Emanuel Bach (C. P. E. Bach). This English version was translated from Japanese one by ChatGPT.
ChatGPT4o writes as follows (please note that it may not be accurate):
Emanuel Bachʼs Fantasia in C Major Wq. 61-06 (H. 291) is one of his later works, characterized by its free form and improvisational elements. This piece showcases Bachʼs mastery in expressing rich emotions, featuring bold modulations and rhythmic changes that surprise the listener. Particularly, the free phrases developed from the beginning demand a high level of interpretative skill from the performer. The complex harmonic progressions based on Bachʼs music theory add depth to the entire work. His pursuit of “emotional truth” in music is vividly reflected in this fantasia.