Have you ever wanted to apply an effect to just one frequency of a track (eg. all high frequencies)? For example, you may want to apply flange to all the high frequencies on a certain track. Here's one way to go about it (I'm sure there are others).

EQ the original source sound into two bands, using a hi and a lo pass filter. Have them set up so that prior to adding any other effects, the two of them have the same frequency response as the original (eg. don't add any colour to the sound). One of the keys to this, it to avoid setting the resonance too high.

Now create a rack, put these into two chains, and effect the band that you want to. Play around with that and see what kind of wacky sonic adventures you can get yourself into.