In this piece the cantus firmus appears again in the tenor range, but is now played by the feet instead of the left hand. In one of Bach's rare registration indications, he specifies that the hymn melody (cantus firmus) be played on a Trompete 8' stop. He also specifies that the three manual accompanimental parts be played on the 8' Principal. The lowest manual part is actually the bass line, which in this piece is usually in a lower written range than the cantus. It should be played on the same manual as the upper two parts, since a large bracket appears in the autograph.
If there is not an adequate 8' Trompete that is playable in the pedal, or if the pedal range does not reach to the highest notes of the cantus firmus, it would be possible to play the entire pedal part down an octave on a 4' reed stop.