So very cool, Steve, music & fractal alike! Wonderful ride, thank you!

One thing: I think a busy fractal like that might do even better with a somewhat calmer background? I noticed at some places that I had short bout of disorientation, my eyes were unsure what to focus on. But of course, might just be me

In any case: one of your best yet!

Ohhh that is one of the most beautiful asurf-vids I've seen! Asurf in candy-land...  Thank you, Steve!
I agree that full-dome might be just awesome with the Thorny one. Also thank you for your workflow explanations, I wish Mbulber wouldn't keep wanting to explode my machine  Otherwise I'd give it a go too

"one of your best yet!" I agree with that. I didn't know MDBB could use a folder of backgrounds. I wonder what would happen if you scaled up the backgrounds relative to the foreground? Maybe the camera would only see parts of the background. But that would equate to more memory and more time to render I guess. You are getting very good at using the mirrorspheres. BTW thanks for naming them
I've noticed that animated fractals 'mutate' in response to the camera position, something that static fractal images cannot show. Your use of the shaking effect enhances this. These animations are highly dynamic which makes them very acceptable as artworks. If anyone knows why fractals change relative to camera position please let me know?

As we get closer to a fractal, we start to see more detail. That's part of the very nature of fractals. The fractal always changes as we get closer to it, if only to reveal more detail that was too "small" to see before. I'm also using a turbulent displacement effect, that is most noticeable when the fractal moves relative to the camera. And fractals exist on a 3D plane and sometimes have to be fully appreciated by flying around and through them.

I often map my way through a fractal scene with everything static, and then run a test. Then I add a parameter like fractal power to the scene, and see how much I can change things from the scene I just made without either bumping into things, or without too wild of a change. Sometimes I see that a stretch of keyframes is pretty much just a long tracking shot and decide to morph the fractal by twisting it a degree here and there, or from 0 to 90 and then to 180 degrees and then back. Everything is still where it was but now it all spins around--hopefully without smacking the camera. So, sometimes the surface is changing because I'm morphing a parameter, sometimes a closer shot will cause the fratal ro render more detail.

"Mirrorspheres" is a tiny bit more elegant than the "mirrorballs" which I used to use. 

I always think the latest video I'm doing is my best, because everything learned on other videos get put into this one. Having said that, I'm always experimenting and trying new things, sometimes to the overall detriment of the video. Sometimes I'm just trying out some things and sometimes things that you do randomly end up looking awesome, and you say, "Ok, more of whatever that was!"