I get the flipping. It happens so quickly that it genuinely entertains the eye and makes it feel like dance... which is one of the reasons why I love optical illusions so much (have been nigh-obsessed with them at times). It's fun and it makes me brain ache in a very pleasant way.

Be-bop is aural negative space
I think you're going to have to elaborate on that one a little more (give me a couple of song examples, if you would - I might already own them, as I went on a massive bebop tear three separate times in my life, the most recent after watching Ken Burns's "Jazz" on PBS that year where I first discovered the pleasures of filesharing).