One of the first Bach fugues I recall hearing was the final movement of his Capriccio in Bb Major, on the departure of a beloved brother (BWV 992). The movement is titled Fuga all'imitazione della cornetta di postiglione (Fugue in imitation of a post horn).
This Capriccio is believed to be one of Bach's early works. By definition, a capriccio relies on fugal techniques. By using Fuga as the title of the Capriccio’s final movement, I wonder if Bach was trying to point out that he had actually written a double fugue!
Enjoy this recording of the Fuga by harpsichordist, Gustav Leonhardt.