It looks like the Height is age. So y-axis, is age of music.
But the left-right categorization, seems arbitrary. I'm curious if it is just arbitrary, since you have to start somewhere. I looked around and didn't find much help on the overall scheme.
EDIT:
I think the overall columns are a best guess based on this
"The Definition of Genre
The history of Popular Music hardly qualifies as an exact science. It is a retrospective analysis of events that focuses on the underlying forces or common symptoms in the overwhelming production of music records, ignoring nuances and side-effects to grasp a comprehensible structure. This is because (popular) music is far from a static phenomenon: it is a constantly evolving, transforming, giant organism. Almost never has a music genre suddenly emerged as a shocking revolution without any trace or evolution in the past. All of them have naturally evolved, mutated, merged, or become (theoretically) extinct. Only the past can be examined of this natural, organic network."
But the left-right categorization, seems arbitrary. I'm curious if it is just arbitrary, since you have to start somewhere. I looked around and didn't find much help on the overall scheme.
EDIT:
I think the overall columns are a best guess based on this
"The Definition of Genre
The history of Popular Music hardly qualifies as an exact science. It is a retrospective analysis of events that focuses on the underlying forces or common symptoms in the overwhelming production of music records, ignoring nuances and side-effects to grasp a comprehensible structure. This is because (popular) music is far from a static phenomenon: it is a constantly evolving, transforming, giant organism. Almost never has a music genre suddenly emerged as a shocking revolution without any trace or evolution in the past. All of them have naturally evolved, mutated, merged, or become (theoretically) extinct. Only the past can be examined of this natural, organic network."