It’s a beautiful and fascinating chart which, rather like our chord diagram, requires the reader to study it for a longer period, perhaps even a few minutes. It might not be as immediately readable as the preceding column charts, but it will tell you more.
Smith, Alan. How Charts Work (pp. 137-138). Pearson Education. Kindle Edition.
Adding the detail on how to interpret the chart
Smith, Alan. How Charts Work (p. 206). Pearson Education. Kindle Edition.