Ultimately, what we will do within ProTools is select say, a snare drum track and duplicate it.
Select "Duplicate Track" within the File Menu or by right-clicking with the mouse/trackball.
You can also select by choosing the hot keys (Shift+Option/Alt+D)
You should now have an exact copy of the original track.
In some instances you may choose to leave the original track unprocessed. For instance, if you have a drummer that is performing a more dynamic part complete with rolls, drags and ghost strokes, you may find it difficult to apply a gate to the track for fear that the performance will be compromised.
With the mult you can process it independent of the original. With this track you can be more aggressive with the compression, EQ and gating.
If you apply a quick attack and short release to the compressor it will give it more pop, which may be what's lacking in the original.
Now you have the best of both worlds.
These mults play a major role in my mixing when I create multiple tracks for bass.
My approach is to allow myself the flexibility of having say, three tracks devoted to a specific frequency range.
We will keep it simple for this exercise and create one mult for the bass (with the two separate tracks set up for the bass solo and the duplicate).
Now, let's assume that you have an organic song with the piano as the primary instrument. The way I approach it is to view the piano as the anchor. I roll off the low end of the piano up to about 100Hz, effectively providing space for the bass to reside.
Play the piano and bass together.
Now what we want to establish is to hold the bottom two octaves below the piano to add size and weight. They should almost feel like one instrument.
Roll the bass off at 40Hz and low-pass it at up to 120Hz.
Now add a compressor, which allows for the bass to be clear and present without overwhelming the piano.
* Remember, we want to create one instrument.
With the original bass track, try rolling off the low end up to 120Hz and low-pass down to maybe, 1kHz.
It may sound pretty absurd, but when blended with the other track you may have something more manageable in the mix.
This comes in quite handy for handling the sub frequencies below 50Hz. Plus you'll still be able to have something that resembles a bass guitar as well.