Bach's Color Wheel in Organ Sonata No. 2

It was the stunning slow movement that “coerced me” to create a piano transcription of Bach’s Organ Sonata No. 2. I just had to play it for myself and I’m no organist. But the outer movements have their own bliss. Here is the first movement. The immediate delights are the trills. Mordents ( short fast trills) punctuate the cadences of the opening theme and recur throughout the piece. But the grand moment is a continuous trill through a dazzling culminating sequence that returns to the tonic and the final statement of the ritornello. But just as remarkable, the entire piece is based on the circle of fifths. Of course, most Baroque pieces use this structure, but Bach always finds a way to give the fifths new color, new dissonance, new urgency to propel forward…