Useful stuff...
And I imagine that many of us will be surprised at how LOW some of these frequencies are. Next time you try to get more clarity in a vocal, don't necessarily reach for the 12Khz treble knob! Or boost 80Hz to get more 'body'!
Fixed mid range EQ mixers are a NIGHTMARE to dial in a good sound with, because that is where nearly everything is! Give it all the same frequency boost, and you end up with mud...
If you can afford it, a mixer with a parametric (or semi-parametric) mid EQ makes all the difference.