The great Baroque composer J.S.Bach was able to take on the roles of composer, performer and teacher, and excel at all of them. The g minor organ prelude is an example of Bach's work for his church, where among other duties he was expected to compose new pieces weekly for the choir. This piece was intended as the introduction to a choral piece of the same name. Roy Bogas' transciption reflects the organ's massive range by imitating the sound of foot pedals (the organ has an actual keyboard played with the feet, in addition to using both hands!) with mostly step-wise base octaves. The polyphonic texture, a hallmark of the Baroque era, is brought out partly by using all of the piano's foot pedals.
Fantasias, on the other hand, were intended as entirely secular and free-form pieces. Contrast and an improvised character are emphasised, with lots of harmonic and rhythmic exploration.