Having mixed hundreds of music projects over the last 20 years, I've mastered using lots of different software. Now my go-to plug-in is the Waves Linear Phase Multiband Compressor. Its sound quality is excellent and the interface is easy to use. This is a tool that's powerful for both quick projects as well as my most serious mastering work.
A great tool for mix - mastering.
Firstly this multi compressor is important because of the linear phase, it won't colour or change phase of your audio. That's super important in mix - mastering.
Secondly it helps to level out your overall mix and fix problem areas such as sub frequencies that swell and reduce head room.
I use the basic adaptive multi preset and reduce about -3db just to smooth out things. It can help you attain a louder mix but use sparingly!
Invaluable Mix Finishing Tool
First off, what makes this MBC somewhat unique and the reason "Linear Phase" is in the name is because a traditional multi-band compressor will "color (i.e. boost or cut) your signal around the crossover frequencies you specify. This can be used to your advantage, if you know what your doing. This version, however, is supposed to be neutral at the selected crossover points and is intended for use mainly on a the master buss during mixing or on a mix master in a mastering session. I feel it accomplishes this quite exquisitely. This plugin is great for that which it was intended. The following is only commentary on MBC in general.
Second, multi band compression, regardless of flavor, has the potential to put a final polish on a good mix/master or completely destroy a mix if used with a heavy hand (or if you don't really have a firm grasp on what a compressor actually does and how it functions). I've learned this from experience and is the reason I have only recently started using MBC in mix sessions again. But, now that I have revisited it, I think that what multi band compression brings to the table at the end of a mix is absolutely amazing when used "correctly". (Which only means that you know how to set it to get the results you were after, or better)
Here's a workflow to start you in the "right" direction...
1. Mix your session as you normally would and once things are in the ballpark regarding balance, EQ, and gain staging...
2. Scale back any compression you may have added to the master buss. By that I mean, you'll be better served if your mix buss compressor is reducing gain by less than 2db at the most and, since you're about to add more compression, you'll want to retain as much dynamics as possible going into the MBC.
3. Depending on the material you're mixing and how you use EQ to make space for things in the mix, the Crossover frequencies and attack settings for each band will vary. Solo each one and listen to what range of each individual track is being represented and adjust crossovers to taste. I find for my mixes that 0-80Hz captures most of the lows (kick and low bass notes), 80-650Hz captures low-mid (beefiness of bass guitar and toms and general muddiness from everything else), 650-3500Hz captures mids (most instruments and vocals), 3500-8000 captures high-mids ("presence" of instruments/vocals and meat of cymbals), and 8000Hz+ captures highs (vocal sibilance, cymbal shimmer, and general "air"). I set the attack based on whether I want to allow transients in each band to come through or be reigned in - 15ms if yes and 2ms if not.
4. Pull the Threshold of each band down until it just begins kissing the gain reduction (represented by a 2-3db drop in the yellow line). Some bands may require more gain reduction than others (i.e. if you're having a hard time taming muddiness in the low-mids, which happens to me quite often).
5. Compensate for the compression gain reduction by adding 2-2.5db of makeup Gain. This is also where you can rely begin to sculpt the spectrum of your mix. I must be mixing in a bright (high-mid/highs accentuating) room, because it never fails that I take a mix somewhere else to reference it (in the car, home stereo, etc.) that it's a little heavy in the low-mids and sometimes lows. So, what I do is either adjust the Thresholds in those band to reduce more, reduce the makeup Gain by a db or two, or both.
What you'll find is that you can sculpt the dynamics and EQ balance of an entire mix with having the compressor mask mids and highs when it invariably responds mainly to low frequency energy in your mix. This will make your mix immediately "seem" brighter because kick, toms, and bass guitar are no longer causing the compressor to mask those bands. Just remember a little goes a long way here. 2-3db of gain reduction and 2-3db variations in makeup Gain will serve you well. Cheers!