Some people have asked me about the score of this piece. Although I'm playing this Canon as well as his other works for organ from the special organ edition which was published just a few years ago, I found this score of Canon in Ab Major in the original piano notation prepared by Stepas Bidva.
If you want to play it on the organ, simply assign the lowest voice (dotted half notes for the most part) to the pedals (soft 16' and 8' stops). The right hand part with the canon sounds best if played with the solo registration on the separate manual (8' and 4' flutes). For the left hand part choose one or two soft 8' stops.