The number of compressor plug-ins on the market is overwhelming. As you'll surely understand, it would be impossible for me to create an complete list here. Nevertheless, my collaboration with Audiofanzine and my "audio geek" side have led me to try out quite a few of them. So, here are my own personal favorites when it comes to software compressors.
I sometimes like to challenge myself and go: "Today you'll mix exclusively with freeware." Whenever that happens, I usually resort to three compressors: Molot, TDR Feedback Compressor II and ReaComp. But don't get me wrong, I also like to use them regularly under normal circumstances, even if I'm not challenging myself. I mentioned my all-freeware challenge only to make the point that it is possible to work seriously using freeware alone.
I use the TDR Feedback Compressor II when I need a soft and transparent compression. ReaComp can handle harder compression while still remaining transparent. Molot, for its part, is a dirtier compressor, in the sense that it adds a particular coloring of its own.
I must admit that the quality of compressor plug-ins has clearly increased in the last couple of years. The difference in terms of quality with the hardware big boys is still there, but it's never been so small. Oddly enough, in the current who-sounds-more-like-analog game, the most expensive plug-ins aren't necessarily the best… Thus, my go-to compressor is the very affordable Klanghelm DC8C 2. If you were to take a quick look at all the mixes I've done in 2014, you'd find the DC8C 2 on 95 percent of them. However, my arsenal has increased with some real heavyweights lately…
On the other hand, when I really need to completely "twist" the behavior of my compressor to process a particularly stubborn track at will, I have recently started to go for the U-He Presswerk.
Finally, the last couple of months I have frequently resorted to the compressors included in the Slate Digital Virtual Mix Rack. Besides sounding very nice, they are easy and comfortable to use, all while remaining relatively low in terms of CPU usage.
I seldom use multiband compressors during mixdown, but if I ever do, there are only two plug-ins that are up to the task, in my opinion. The first one is none other than the FabFilter Pro-MB, whose versatility is unmatched.
The second one is developed by the Frenchmen at Blue Cat Audio: The MB-7 Mixer 2. Strictly speaking, it isn't a true multiband compressor, but it allows you to split the frequency range into several bands and apply to them any third-party plug-in you see fit! In other words, you can create the multiband compressor of your dreams by combining your favorite compressors!
And that's it for today. Once again, this list was based on my own personal tastes, and there are heaps of other excellent choices available. It's up to you to find the software compressors that work best for your music.