This is something I've been coming around to over the last couple years. I "understood" compression for several years (the theory behind it), but never nailed down how to use it that well. What changed for me was sitting down with several different compressors to learn their different sounds so I would actually use them with purpose.
It's difficult when you're learning electronic music because everything is so in your face. The forum mentality a lot of us learned through can be hard to navigate. You'll find dozens of threads with subjects like "What's the best/your favorite compressor?" and not enough "What compressor will help me round out low, female vocals?"
I'd go through phases of using the fabfilter pro-c on everything cause Madeon said he used it, then phases of using ableton's stock compressor because Feed Me said it's all 99.9% of producers will ever need, then H comp cause Skrillex etc... What I've come to realize is that pretty much every producer I obsessed over was still learning how to do all of this shit themselves-they just managed to make really good music while doing it.
So I'd recommend every producer find the range of compressors that work for them so each instance is used with intentionality.
ok i understand that and the theory behind it. what i dont understand is if i put compression on one channel i.e female vocals - how does it compress it in relation to the other channels?
I don't know if I 100% understand exactly what you're asking. If you're dropping a single compressor on a single channel you'd only be reducing the dynamics of the single track (vocals in this case). How it plays into the overall sound depends on how you treat the rest of the music.
You use compression if you know that the sound needs it.
I like a little bit of compression on some things, but i tend to not use it willy nilly.
I compression a source with many effects coming from some kind of effect rack or combinator (ableton and reason respectively), if it needs the glue.
Compression can also help a group of parts (ie drums) sound as if they're moving as one unit (glue). it helps shape and tailor the impacts and notes to a song a little bit better. or to help get a certain feel and sound out of a specific set of instruments.
so if i want to compress my drums i would group them all (in ableton) and use a glue compressor or whatever i prefer (parallel, etc) and get them to sound closer together basically instead of some peaking where i dont want them too.
or what you think?
This depends on the sound you're going for. If you just want to bring the drums together a little bit some light compression may get you there. At the same time if you send any effect to the whole kit you'd likely get a similar result. I'd recommend gain staging to even out levels first though. Even using something like Waves Vocal Rider. Especially when you're using more organic sounds...compression can be unkind really quickly. Even if you're diligent about using it more subtly, I've gotten to the end of a lot of mixes and realized how much life was sucked out of the song compared to the initial garbage mix.