A Level Music Technology

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10 Dynamics processing

This page is an overview of the content for this topic; enough for revision or to get you started. For more in depth explanation and diagrams, you can purchase the full course here. The small fee for the full courses supports me keeping the website running.

Compression

  • A compressor sets a level (threshold) above which the compressor reduces the volume by an amount (ratio)
  • Compressors reduce / narrow the dynamic range; we hear this as the track being more even or consistent in volume with fewer peaks jumping out of the mix – this happens in two stages:
    • It pushes down the peaks i.e. reduces the volume of the loud bits of a track that are above the threshold
    • The signal is now much more even in volume but is quieter overall than it was because we’ve made the loud bits quieter; the compressor then raises the volume of the entire signal using the make up gain
  • Extreme compression can make the signal sound like it is ducking and overemphasise quiet sounds like breaths
  • Compression can be used musically to add rhythm – sometimes called pumping, for example in EDM
  • Limiters are compressors with an extreme ratios (∞:1) used to prevent signals from increasing beyond a level
  • The threshold is the volume above which it begins to compress in dB (low = lots of compression, high = little)
  • The ratio is the amount of compression; once above the threshold it is the ratio in:out (high = lots, low = little)
  • The attack time is how quickly the compression is applied once the signal goes above the threshold; a fast attack pushes down the initial transient and a slow attack maintains the transient
  • The release time is how long it takes for the compressor to stop compressing once the signal is below the threshold; a short release increases the amount of sustain – a slower release means less sustain
  • Peak and RMS are different ways the compressor analyses whether the signal has gone above the threshold
  • Peak mode reacts to the signal’s momentary amplitude; it can catch fast, transient peaks
  • RMS (stands for Root Mean Square) is based on an average; it misses sudden peaks but is generally more natural
  • Sidechain compression is where a compressor is triggered by the volume of one track, but is applied to another
  • A deesser reduces or eliminate sibilance by compressing only the sibilant range of frequencies via a sidechain.

Gating

  • Gating silences anything below the threshold; it can be used to remove noise or quiet sounds from a recording
  • You might use a gate to remove distorted guitar amp noise or movements or noise between vocal phrases
  • A gate only silences quiet sounds in the gaps between playing, not when other things happen at the same time
  • You might not want to completely silence the quiet bits; we can use expanders to make them quieter
  • When above the threshold, the signal opens the gate; when below, the signal is silenced by the gate
  • Reduction / range is the amount of volume the signal is reduced by in an expander – often completely in a gate
  • Attack is the amount of time it takes for the gate to open once the signal goes above the threshold
  • Hold is the time the gate stays open for after the signal drops below the threshold level; used to avoid chattering
  • Release is the time it takes for the gate to close once the signal is below the threshold and hold has passed
  • Lookahead controls how far ahead the gate analyses the incoming signal, allowing the effect to preempt peaks
  • Hysteresis provides another option for preventing chattering; it sets an upper / lower range for the threshold
  • A noise gate or expander can also be controlled by a sidechain; this is also known as a ‘keyed gate’.

Loudness

  • We use the term ‘perceived loudness’ or ‘perceived volume’ to describe how loud something seems to us
  • Modern recordings (particulary chart music) are louder than older recordings and have less dynamic range
  • In analogue technology like tape and vinyl, having a loud track helps to mask the noise inherent in those formats
  • The loudness wars refer to the trend of making recorded music louder and more compressed over time.
  • The trend began in the 1990s and peaked around 2005, and was audible in remastered music and new releases
  • It leads to a loss of detail, warmth, and dynamic range in the music, sounding distorted, flat and fatiguing
  • LUFS stands for loudness units relative to full scale – how loud a recording is compared to the maximum volume it could possibly be (i.e. 0dBFS); some streaming services now measure LUFS as part of loudness normalisation

The impact of dynamics processing

  • Compression adds impact and punch, particularly to percussive sounds, and simplifies mixing
  • Compression makes it possible to increase the perceived loudness of a release and consistent level in its tracks
  • This can lead to overprocessing; overcompression can lead to a lack of dynamic range (loudness wars)
  • Overcompression can increase masking and reduce clarity, and lead to listener fatigue (no light / shade)
  • Gating makes it possible to automatically remove unwanted noise and noise buildup in between phrases
  • Having lots of control with gating and compression can lead to a relentless pursuit of flawless music
  • The overuse of dynamics processing has been widely criticised by music producers, engineers, and enthusiasts.