Compression Part II: Applied Concepts

Makeup Gain: Makeup gain can often be used and abused improperly. Many producers will employ makeup gain in attempts to raise the levels many of the lower level signals, signal that might not even be affected by the compressor. Doing this puts us in danger of raising our noise floor to unacceptable levels, and adding hiss and hum to our track. Makeup Gain is essential for returning our compressed signal back to its original levels. This is very effective for adding punch to drums.

Side chaining: Side Chaining is a crucial tool for both mixing and production purposes. When a compressors SideChain function is activated, you will often be prompted to select an input. Once selected, your new input becomes the new signal that we will be monitoring. As the new input signal reaches past the set threshold, our original signal is compressed accordingly. This is a very common effect in dance music, where with careful manipulation of the attack and release of a compressor, a synth patch can be side chained to a kick drum, giving the song that push - pull effect that is so essential for creating groove in a track. 

Multiband Compression: As you delve deeper into the world of production and mixing, you may encounter more complex plugins that employ Multi-band Compressors. A Multi-band compressor might look intimidating, but with the concepts that we've learned already, we can pick it apart quite easily. A multi band compressor might look similar to your multi band EQ of choice, only now, each of the frequency bands that we have at our disposal, treats it's frequency range as a compressor, meaning that we can compress and attenuate specific frequency ranges of our track. This is very useful when making those microscopic touches to your mixes. 

Parallel Compression: This is a concept that many a internet scholar hath written upon, and there is no easy way to go about explaining it.
Here is the main gist of Parallel Compression: Our goal with Parallel compression is to make a track more present in our mix. While a beginning producer might believe this effect can be achieved just by turning up the volume of their track, or compressing harder and applying more makeup gain. Doing either of these would drastically increase the level of our noise floor.

So our goal is to achieve a louder sound without
a): Squashing our louder sounds                                                                            
b): raising our noise floor to obscene levels

We do this by splitting our signal into two paths. One remains unaffected, while we run the other through a heavily attenuated compressor (through an aux track or a send) The goal of this compressor is to completely squash our louder signals, we're talking heavy ratios and low thresholds: -20 dB to -30 dB is a good start. This means that to achieve proper, clean sounding parallel compression, we're going to need to use a compressor that can handle heavy amounts of compression without distorting the signal too much.
This effectively leaves our quieter signals that are below the threshold unaffected, while heavily compressing all sounds above the threshold

The final result is both of these signals blended together.

Doing this has achieved two things:
1: By applying heavy attenuation to the louder ends of our compressed track, we've prevented our overall levels from getting out of hand
2: We've allowed our quieter signals to become louder simply through the combination of the 2 signals (the un-altered original signal, and the "below the threshold" signals of our compressed signal) This has essentially just applied a form of "makeup gain" to our quieter signals.

Through careful adjustment of our various stages of gain, our thresholds, and our ratios we can achieve a sound that is perceived as louder, punchier, and more present, all without distorting or squashing the signal, and without introducing the hiss of a overly boosted noise floor.