Picture a sine wave it's a single frequency lighting up in the EQ, then add harmonics, it could be another layer it could be distortion it could be a detune it could be fm. once you add harmonics the timbre changes, if the sound is balanced the profile will look flat-ish in a spectrogram if it is unbalanced some parts will be quieter than others if it has too much bass it will just sound like Bass if it has too much mud (100 to 300) it will not sound good, this is not a great frequency range. if it has too much low mid it will sound dull if it has too much mid-range it will sound harsh and irritating if it has too much high-mid in the presence range it can also sound harsh but you can push it harder here. if you have too much air it will also sound harsh and be very irritating and give you a headache
- when you go to processes sound you need to know what your intent is with that sound before you decide which section in the frequency spectrum to accentuate with compression or gain
- I usually compress the main section of the sound's frequency depending on the timbre of the sound to make it very thick and then balance the other two bands with gain. (and compression on the secondary bands IF it has lots of dynamic range or resonance.)
- cutting, when a sound has multiple harmonics playing they all interact in a certain way. when you take away some of these harmonics the other ones are able come through with more clarity. After you've gone through and balanced the sound with multi-band compression and shelving eqs try to cut what you don't need. If it's a bass sound I usually try and cut the mud between 100-300 HZ. If it's coming across irritating or harsh I try cutting the mid-range 1000 to 3000
- boosting, when you boost a sound with a narrow band you get what is called a resonance if you boost a resonance high enough the sound will start to actually change because that resonance is dominating all the other frequencies idk thats just what I think(?) if you make the band too narrow it gets a little bit screechy and irritating but if the band is wide enough and boosted a little bit it can actually make the sound interesting you can try and boost in the low mids and also in the upper mid-range to simulate a vowely formant sound.
- boosting multiple resonance peaks at the same time is kind of what a comb filter is doing, like is Serum, but it can also be overdone and you need to find the sweet spot with a comb or phaser filter with high resonances.
This is all I know for know just based on my observations and experience >:D