Passacaglia on the chorale 'Komm, Gott Schopfer, Heiliger Geist' by J S Bach is based on a chorale melody derived from the famous plainsong hymn Veni Creator Spiritus. This is the 'ground bass' on which this Passacaglia is built. However, like many Passacaglias in the Canonic Repertoire, the theme often strays into the upper voices of the texture, and because of the relative length of the theme, it has something of the sense of a set of variations as much as of a Passacaglia. The chorale melody modifies the plainsong melody somewhat by moving it's third cadence from the sub-dominant to the dominant, thus creating something of a sense of the confluence of authentic and plagal modes. In some variations I have modified the tune further, to create Phrygian and other modal structures, authentic and plagal. Finally, each of the 12 variations bases the melody on a different tone-centre (plus it's authentic or plagal structures): encompassing all 12 tone-centres (B-flat, E, F-sharp, E-flat, F, A, D, C-sharp, G, A-flat, B, C) over the course of the piece.