I'm having a hard time understanding what Compressors, limiters, Multi band compressors, and gaters are and how and when to use them.

Can anyone point me in the right direction to tutorial you feel does good job of explaining them?

 

Compression is explained in some depth here https://theproaudiofiles.com/compression-techniques/

Well explained basic limiting here:- https://music.tutsplus.com/tutorials/a-beginners-introduction-to-limiters--audio-1071

Here for multiband compression - http://media.soundonsound.com/sos/aug02/articles/multiband.asp

This one will explain how to and when to use a gate http://www.behindthemixer.com/audio-gating-guide/

 

Each have their practical applications (limiting dynamics) as well as esthetic applications (warming the sound, adding favorable distortion, etc...).

Multiband compressors are best left alone by beginners as you will likely be doing more damage than good. They are most useful for the mastering stage to fix problems in an already mixed down audio file.

Limiters, or any kind of extreme compression, is really only needed on very percussive instruments with sharp transients at the mixing stage. At the mastering stage they are often abused to compete in the loudness wars...

Gates and expanders are often useful for mixing drums sets (i.e. removing the other sounds of the drum set from the individual mics) or reducing noise in tracks. You have to be extremely careful with the settings though, so as to not cut off any transients or the instrument's natural decay.

As for the practical applications of compression. You always have to weigh in your mind whether a fader move, volume automation, equalization, or any number of other mixing moves would produce a better result than just slapping a compressor on a track and squashing it. Avoid the temptation to just squash something to make it more present in the mix.

Different types of compressors (FET, Opto, VCA) each produce a distinct sound as well and many are flattering to particular instruments. That is where the whole esthetic side of applying dynamics processors to tracks comes into play. Sometimes you will decide to run a track through a vintage compressor and not have it impart any gain reduction just so the transformers can apply some lovely distortion to the signal.

 

Ok i'm starting to understand a little.

What is transient? I googled it. "In acoustics and audio, a transient is a high amplitude, short-duration sound at the beginning of a waveform that occurs in phenomena such as musical sounds, noises or speech."

To make that simplier, is it the first "Attack" sound that an instrument makes?

For some reason when I use a compressor and compress an audio and then increase the gain. I don't hear the flattening that you speak of. Do my ears need to be train more?

I use limiters sometimes like the Fab Filter PRO L and use it to increase the volume on sounds that are too low in a mix. instead of increasing the volume knob when I feel the volume is already too high. I'll increase the limit knob and then lower the volume knob. Is that a good practice?