In the studio, compression is probably the most important tool in an engineer’s arsenal – both in the mix and during tracking sessions. Properly used, compression can bring elements forward, fit them in the mix, shape tone and timbre, and glue mixes together.
In a live setting, compression isn’t as ubiquitous, at least in smaller set ups. Still, the judicious use of a little compression can be invaluable in bringing together a great stage sound.
What is compression?
In case you haven’t had a primer on compression, here’s a quick definition: Compression lessens the difference between the loudest parts of a signal and the quietest. All this really means at the end of the day is that a compressor turns down the louder parts of a track or live signal (a vocal mic, for example). You can then turn the whole signal up louder, and the result is you’ve now brought the quietest parts up – effectively “compressing” the dynamic range of a signal.
Settings on a compressor include:
- Threshold – Determines at what level to start turning the signal down
- Ratio – How much to turn down the signal
- Attack – How fast to turn down the signal
- Release – How fast to go back to normal
- Knee – Either soft or hard – Hard means the transition between compressed and normal signal is abrupt. Soft means it’s gradual.
- Make up gain – How much to turn the entire signal up so that the uncompressed parts are now louder in relation to the whole.
Think of compression like a very fast android who turns down the fader when the signal gets too loud. You tell the android how loud the signal can get before they turn it down (threshold), how much to bring the fader down (ratio), how fast to react (attack), and how quickly to bring it back up when the incoming signal is back under the threshold. If the compressor includes a “lookahead” feature, then your android is psychic and can turn it down in advance.
Less is more
In a studio setting, compressors can be used a number of ways, including very aggressively, subtly, multiple compressors in line, compressors on the final mix, and so on. In a live setting, you’ll probably be limited by the number of physical hardware compressors you have so you won’t be able to line up multiple compressors or use them on everything. There’s also plenty of reason to be a little more judicious with compression on stage.
Chief among those reasons is that when you compress a signal – let’s say the vocal mic – a lot of previously unheard noise may now come through. This could include loud stage amps, drums, monitors, bar noise, and more. In addition, an aggressively compressed signal is more likely to feedback.
If your stage sound is very clean, you’ll have more room to compress without trouble. So, it’s a good idea first to clean up your stage sound as much as possible. Reigning in drums, repositioning amps, moving toward in-ear monitors, and turning down your overall stage volume are all ways you can start to do this.
What to compress
On stage, the number one candidate for compression is the lead vocal. Many vocalists have such a wide dynamic range, and the vocal sits in basically the same frequency range as guitars, so getting the lead to cut through the cacophony of band and crowd is your number one goal.
Just be sure not to go too wild, as an over-compressed vocal might sound thin and lack robustness. Also, try not to send the compressed version to the vocalist’s monitor. Instead, send the raw signal (with reverb if the vocalist prefers and its available). A compressed vocal signal in the monitor can give a vocalist a sense that they’re not getting loud enough, and they may tend to strain, damaging their tone and putting their vocal cords at risk.
Kick drum can also be a good candidate for compression in a live mix, since kicks can sometimes have trouble cutting through enough, and they’re crucial for establishing the groove.
Many engineers like to compress the bass, as well. Subtle compression on the bass can help smooth out uneven notes and glue the groove together.
Guitars are rarely compressed in live settings. Guitar amps and pedal boards tend to compress these signals anyway, especially when they’re distorted, and other than the drum kit, guitars are usually the one instrument overwhelming others. Acoustic guitars are prone to feedback already, so compressing an acoustic is likely to exacerbate that problem, but a very light touch could give them some extra character and oomph.
At the end of the day if you have one compressor, use on the lead vocal. If you’ve got no vocal, then listen to the mix – you may not need to use compression at all.
Compression is a vital tool in recording studios and plays a key role in live situations as well. In a live situation, just as in the studio, the number one rule of compression is to listen rather than setting and forgetting. Used with care, a good compressor can take a live set to the next level.
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