The postlude provides a sharp contrast. It is brisk and lively. Written by Johann Sebastian Bach (1685-1750), it is the third movement of his Trio Sonata No. 1 in Eb major. The unique feature of a “trio sonata” is that each hand plays a distinct melodic line, while the feet play yet another bass line. This results in playing three lines of music on two keyboards and a pedalboard with all four limbs, a challenging task. What might otherwise be done with three separate instruments is done here all on one instrument, a wonderful demonstration of the organ’s musical capacity.