This site introduces unknown Emanuel Bach (C. P. E. Bach).
ChatGPT4o writes as follows (please note that it may not be accurate):
C. P. E. Bachʼs Fantasia in A Major Wq. 58-07 (H. 278) is one of the works that showcases his unique style. This piece is characterized by its free form and improvisational elements, offering performers a great deal of interpretative freedom. From the very beginning, the piece unfolds with emotionally rich melodies and bold harmonic progressions that captivate the listener. Particularly, the contrast between rapid passages and slower sections is striking, leaving a strong impression on the audience. The depth of emotion and technical skill evident in Bachʼs works are prominently displayed in this fantasia as well. It is a piece that allows one to fully enjoy the wide range of expression in his music.