A drawing by Jahnn for his work restoring organs.
My friend Anthony tried to explain the image to me: "The letters represent notes with middle C obviously being in the center. Yellow lines are octaves, red lines are thirds, and blue lines are fifths. Where these lines intersect the grid is a note of relative distance to C. This is a spatial representation of the ratios that determine pitch in the western tonal scale." And when I still didn't quite grasp it he helpfully added: "You know how the frets higher up on the guitar are closer together, less distance between tones? As the pitch goes higher and higher and approaches infinity the space between these frets would get proportionately smaller as they approach zero (that is represented at the top of the pyramid in this diagram). Well there is a ratio that determines how this distance affects pitch and I believe that this diagram represents these ratios geometrically for certain modal scales that deal in octaves, fifths and thirds."