I can't think of a way to do this without some heavy scripting which I know nothing about. However, back when particles were new in AE, I tried to change the properties of Particle World's emitted items. You can change the properties of the next particles in the birth process but you can't change the velocity of those already created. You can change the physics of the world by, say, altering the viscosity or gravity of the medium through which the particles are traveling so slow them down but you can't sped 'em back up again. That is, they're not independently controlled objects in Particle World. A more complex or sophisticated 3D app might be able to allow you control individual elements like those created by a flocking generator.
Umm, I've never used Particle Palyground in the 25 years it's been around and I hear it's highly under appreciated. Maybe you can alter velocities there. Dunno.
So, what I ended up doing 15 years ago was creating a series of movies of particles and then altering the frame rates of the movies, speeding them up and slowing them down. That illusion probably isn't what you're looking to achieve.
Hope someone else chines in with a more valuable suggestion.
Yeah I thought about doing the same thing, but my video's about 8 minutes long, and that means i'd have to copy and paste the clips and line em up with the beats. Not a fun process, but I guess that's how it has to be. Maybe there's a plugin out there that speeds up the particles every x seconds... dunno, but thanks for your help.
Edit: If anyone else needs an example of what I'm talking about, I found a video from this guy on youtube. If you pay attention to the "stars" in the background, they move between the snaps and the beats. [Future Bass] - Sushi Killer & Kevin Villecco - Anime Bae [Monstercat Release] - YouTube
Wish you had included that example, would have saved me lots of speculation.
Those aren't particles, it's just an effect called Starfield. The background movie was simply time remapped to change the speed it plays. I didn't detect any synchronization; the speed changes looked random to me.
The speed of the stars bumps up a notch between the beats. I can't get to my AfterFX right now but I'll try that asap. Thanks.