Whenever I’ve made dubstep style modulating synths on computers, the cutoff has almost always been the thing modulated to provide the changing sound, but as guitarists and bassists we don’t really have that feature as we make our sounds in a different method.

I’ve thought about it though and I reckon that the best method would be probably to link up a few pedals together, maybe a fuzz for some grit and some kind of phaser/flanger? something that would modulate the sound. As for changing rates, its kinda hard unless you find an expression pedal or have many of the same pedal.

Also the thing is that the sounds dubstep artists make are often made up of many different oscillators providing lots of different frequencies, thus making the massive sounds, it’d be kinda hard to accurately replicate that on guitar or bass without some very complicated equipment.

Try things out though, ask at a guitar shop or something, they might be able to help.

Hope that helped mate.

just got the stereo pulsar delivered today, after playing with it for a while i’m so in love, you can do so much! subtle trems to classic EHX craziness, gotta love it! Probably already my fave effect in my board even after a small playing sesh!