Note: "Split the signal" means work with
two separate, exact copies of it. Then processing them separately in different ways . (duplicate track in Pro Tools will give you a 2nd copy, or if you have a patch bay with 'parallels' or 'mults' you can get more copies there)
There were several posts following Tony's tip above asking if multi band compression (plug in or hardware) would do the same job. The answer is -
No, it wont do the same job - that would only do a multi band compressor job.
Yes multiband compressors can be very useful to tame difficult to work with sounds
but the set up Tony is referring to is a
far more advanced and
custom designed technique that gives better control (like the ability to fade up one of the processed signals in a verse or down in choruses etc....) Its worth spending time experimenting with yourself - This is a good example of advanced mixing tricks that mixers develop..They very often work with duplicate tracks - process them very differently and the final sound is a blend of those separately processed tracks. A mixers 'skill shot'.
As Tony says phase is essential - so go study up on it (but not in this Q & A forum)