Mix-buss compression can be a confusing for those who are unfamiliar with how it works. Some producers throw it on every track to make it punchy, others prefer to keep the buss pure.
If you are going to use mix-buss compression don’t just throw it on at the end, start from the beginning of your mix process with compression on the stereo buss. Each fader change will affect the overall sound, if you throw on compression at the end of mixing the overall balance of your track can be thrown off.
Hardware or Software?
If you prefer to go the hardware route there are some great compression units out there. Just like how different mic pre-amps lend their own sonic character during recording, compressors also impart their own signature on a track. I’m a fan of Universal Audio’s hardware and software compression plugins. These aren’t “transparent” in color but for the type of music I usually work on they add a pleasant sonic quality.
A good way to find your initial compression settings is to watch the meters on your compressor, they should bounce nearly in time with the tempo of the track. If they are going faster you release time may be too short, if they are staying pinned the release time is probably too long. Attack time is a little more straightforward, the faster the attack the sooner the compression will kick in during the attack portion of the sound. Having a slower attack time will let more transients slip through but it may not work for the material you are mixing. Conversely, too fast of an attack can often leave a track dull and flat sounding. Once you are used to listening to how compression works you can trust your ears to tell you if there is too much. You’ll hear an audible pumping, if you hear this you’ve often gone too far unless it’s for a special effect.
For overall stereo buss compression you can usually leave the ration pretty low, 2:1 or 1.5:1 are a good place to start. Then adjust the threshold so you get a minimal amount of gain reduction. Less is more when compressing the mix buss.
A common mistake most inexperienced mixers make is just throwing on stereo compression to the mix to make their mixes louder to match commercial recordings. If you are going to get your finished tracks mastered I highly recommend against this. Mastering engineers usually add additional compression during mastering and if your mix is already brickwalled it makes it much more difficult to get a decent mastered track. Instead of having one massive stage with lots of compression, split it up. Put some slight compression on the individual tracks. Then some mix buss compression. Finally in mastering put on another level of compression. Three smaller stages of compression will always sound better than one massive stage. I would also avoid throwing on multi-band compression on the mix buss. If you find your track needs it, you’re probably better off going back and fixing the EQ and compression settings per individual track first.
I hope this gives a little insight into how compression on the stereo buss should be used. Happy mixing.