To express these relationships, I envisioned a type of flowchart, almost like an evolutionary diagram or family tree, showing how music has progressed and how new genres developed from others over time. I tried to find something online that was both visual and comprehensive but without much luck. The closest thing to what I had in mind was popular music scholar Reebee Garofalo’s “Genealogy of Pop/Rock Music”, which you can see below.

This was a start, but still not the ideal expression; for starters, it includes the use of artists to guide the flow, which is more information than I needed to see explicitly for my intent. It’s also a bit conservative in the sense that it only uses the most high-level genres, not distinguishing where there are sometimes popular sub-genres; it only shows about a dozen "rock" movements between 1955 and 1978. And therein also lies the most glaring issue: Garofalo’s genealogy stops, probably for good reason, at a vital period in rock and roll history. The development of punk and heavy metal in the mid to late-70’s and the diverse explosion of work that stemmed from them is incredibly dense and difficult to decipher, but no less important to understand than the invention of rock itself. If I wanted to see the complete visual diagram of the evolution of rock and roll from its origins to today, I would have to make one myself.
After many, many, many hours of work and research, this is what I came up with:

A few disclaimers: you might notice that not everything you’ve ever heard of is there. For the sake of clarity and my own sanity, I decided to limit this to only the development and evolution of rock and roll and it’s most well-known and pure-bred descendants. If I tried to, for example, include a parallel development of soul music into things like (contemporary) R&B and hip-hop, and then depict any integration of soul with rock… let’s just say it would be incredibly difficult and the illustration wouldn’t be pretty. The same can be said for if I had tried to include every genre of “rock” ever made, such as the dozens upon dozens of genres of heavy metal that apparently exist (Viking metal, anyone?). I did include a degree of folk and country, as these are more closely related to rock and roll and I felt contributed to the overall picture rather than hindering it. They aren’t nearly drawn out to their full extents, though. As far as the “boxes” are concerned, the idea is that they correspond with my interpretation of the time periods when genres came into being as unique movements; they’re not intended to show the length of those movements.
The final thing to mention is that obviously this is represents a massive generalization with the purpose of trying to understand something immensely complicated and perhaps in a way that it isn’t meant to be understood. Clearly this is not a science, and as someone who is creative myself, even I don’t like the idea of trying to align the creative efforts of thousands into a neat little diagram with boxes and arrows. However, such methods are often a necessary evil when trying to communicate complex subjects or ideas in a concise and useful way. What it is to write about music, particularly in the sense of critiquing, is to try to describe in words what something sounds like. When one tries to wrap their head around this, trying to take the very characteristics which make one medium truly unique from others and attempting to portray them in another medium, and in an absolute way, the idea is absurd. Just like I could never write a melody that would allow you to see what the Mona Lisa looks like, I could never write a review that allows you to hear what Lou Reed's Transformer sounds like. What I could do is compare it to some sort of foundation, central points from which I can then weave, at the very least, a notion. But like the diagram I’ve presented, that notion will still only be based on my own interpretations and experiences, and you’re better off listening, or discovering, for yourself.
Please feel free to add your own comments, however positive or negative, this is a work in progress, not my Gospel word.