Canonic Variations on "Vom Himmel hoch da komm' ich her"
At the beginning of this variation, the canon is simply the melody of the chorale. It is played by the right and left hand, but this time the left hand plays it upside down (inversion).  It is a “canon at the sixth” (the right hand starts on C, then the left hand starts on the E below).  Later it becomes a canon at the third.   The pedal simply plays a bass part (like a continuo instrument).