These references are general ideas for where to begin to look for sonic issues with particular sounds, instruments, and voices.
~ http://blog.sonicbids.com/the-ultimate-eq-cheat-sheet-for-every-common-instrument
This is cool! I think Jon Sine published a graphic for this a few months ago :)
there's this https://www.audio-issues.com/music-mixing/all-the-eq-information-youll-ever-need/ (https://www.audio-issues.com/music-mixing/all-the-eq-information-youll-ever-need/)