Compression is all about controlling the peaks and troughs (dynamics) that occur in your mix when, for instance, the quieter vocal moments are drowned out by the guitarist during recording and/or playback. In a nutshell, it squashes the loudest peaks and boosts the quieter troughs, meaning you can up the overall track volume to get that extra punch.

Another technique: punch the guitarist!

Compressors in Music

The compressor belongs to the 'gain-based' family of musical effects.

Its uses can be both "correctional" and creative - a correctional example might be for maintaining the trailing sustain of a guitar note where it might otherwise tail-off too early below other instruments in the mix (the sustained note of a guitar falls naturally in volume the longer it's held; the compressor can act to keep it prominent in the recording).

Creatively, you could use it for what's called, 'gain-pumping'. Commonly used in dance music for adding extra punch to the kick drum, the initial thud is "pronounced" by the compressor before being quickly released.

Let's have a look at the common parameter settings to play with.

The parameters:

There are five basic controls that shape the way a compressor manipulates a sound input.

Threshold

Sets the decibel ( dB ) threshold to the level at which the compressor begins to work. If you set it to 10 dB for instance, any signal coming in above that will be have its ass shaped by the compressor according to the parameters below.

RATIO & THRESHOLD EXAMPLE If you set a threshold of 10 dB and a ratio of 10:1, a raw 20 dB signal would effectively be squashed down to 11 dB.

Ratio

This sets the amount of compression, in dB, applied to a signal once it violates your pre-set threshold.

A ratio of 4:1 will output 1 dB for every 4 dB of input signal that exceeds your targeted threshold

Attack

The time, measured in milliseconds (ms), it takes for the compressor to reach its maximum level on the sound.

A fast attack can be useful for damping percussive peaks so the overall track level can be increased. Can also add punch to a track.

Release

Controls how long (ms) it takes to release a signal from the compressor once it dips below your specified threshold.

A long release time can be useful for adding sustain to a signal - on guitar solos for example.

Output

Sets the overall output level of the effect (dB). This can be useful to whack up the output level again after its been reduced from applying compression to a signal - this is otherwise commonly known as make-up gain.

Compression parameter guidelines for popular musical instruments. Attack Release Threshold Ratio Knee Full track Fastest possible Fastest possible or Auto -5dB to -9dB 2:1 to 3:1 Soft Drums 5ms 10ms or Auto -15dB 5:1 to 8:1 Hard Synth Bass 4ms to 10ms 10ms -4dB to -8dB 4:1 Hard Real Bass 4ms to 10ms 10ms -2dB to -10dB 8:1 Hard Vocals Fastest Possible Lowest possible or Auto -3dB to -8dB 4:1 to 12:1 Soft Brass Instruments Fastest possible Fastest possible or Auto -10dB to -14dB 2:1 to 8:1 Hard or soft Guitars Fastest Possible Fastest possible or Auto -10dB to -14dB -8dB to -14dB Hard or soft

Now you know enough to get started but in part 2 of this compression in the mix tutorial, TheWhippinpost will reveal some of the more advanced options your compressor might offer.

Coming soon: Compression in music - Advanced!