I was wondering if anyone had a list of an instrument's unnecessary frequencies

shelving and pass filters are your best friend!
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Generally guitar <160 Hz.

You can always drag a shelf up and down the spectrum until you can hear it. Move it back down again to where you can't hear it. Repeat for each track, and this will cut the bass noise.

Cutting "mud" is not a bad idea, either. Mud is 200-500 Hz (or thereabouts). Drums in particular can be thinned out like that. Just experiment. You can generally cut without causing too much trouble, it's when you boost that you run into phasing and other weirdness.