An artist friend of mine, Howard Penner, made a cleaned-up version of this diagram in Illustrator, for an unpublished paper that another musician friend wrote about it. [1]
I can't find these papers by Hafez Modirzadeh [2] online, but there are some other papers with references to them:
"Spiraling Chinese Cyclic Theory and Modal Jazz Practice Across Millenia", Journal for Music In China. (II:2). 2000
Book Review for In The Course of Performance: Studies in the World of Musical Improvisation. Journal of the Society for Ethnomusicology. (XLIV:1). 2000
"Spiraling Cyclic Theory and Modal Jazz Practice: The 60-Tone Case of John Coltrane and Ching Fang", SEM Conference Paper (Nov. 20), Austin. 1999
This drawing shows a closed cycle covering five octaves. But musical pitches are not a closed cycle, they keep going down and up from there. How can you take this drawing and extend it to an arbitrarily high or low pitch? Make it a spiral.
What you're seeing is a spiral at an angle orthogonal to the angle of view. Imagine a spiral curling around the Z-axis, and a viewer looking straight down Z. The arms of the spiral aren't visible because they are occluded.
I can't find these papers by Hafez Modirzadeh [2] online, but there are some other papers with references to them:
"Spiraling Chinese Cyclic Theory and Modal Jazz Practice Across Millenia", Journal for Music In China. (II:2). 2000
Book Review for In The Course of Performance: Studies in the World of Musical Improvisation. Journal of the Society for Ethnomusicology. (XLIV:1). 2000
"Spiraling Cyclic Theory and Modal Jazz Practice: The 60-Tone Case of John Coltrane and Ching Fang", SEM Conference Paper (Nov. 20), Austin. 1999
[1] http://imgur.com/gallery/oJKln
[2] http://radiodecibel.nl/index.php?page=artist&id=Hafez%20Modi...