Mixing: Dynamics
Dynamics are changes in level, from a drum's sharp attack to a quiet verse and loud chorus. Compression adjusts gain automatically in response to the signal. Use it for a clear task, such as controlling peaks or changing the balance between a sound's attack and tail.
- Define the task
- listen beyond loudness
- compare the attack and tail
Where you run into this
- Mixing
- Recording
- Sound design
What does a compressor do?
A conventional downward compressor reduces gain when the detected signal level exceeds its threshold. The ratio determines how strongly levels above that point are compressed, while attack and release shape the response over time.
Consider an ideal steady signal with a hard knee and a 4:1 ratio. If the input is 8 dB above threshold, the output settles at 2 dB above threshold before makeup gain. That is 6 dB of gain reduction. Real musical attacks also depend on the detector and timing controls.
Which control should I reach for?
| Control | What it changes | What to listen for |
|---|---|---|
| Threshold | The level region where compression acts | Which notes trigger reduction? |
| Ratio | Strength of compression above threshold | How much do louder notes stand out? |
| Attack | How quickly gain reduction develops | Is the initial hit preserved or softened? |
| Release | How quickly gain recovers | Does the sound recover naturally between events? |
| Knee | How gradually compression begins around threshold | Is the transition subtle or abrupt? |
| Output or makeup gain | Level after processing | Is the comparison louder rather than better? |
Exact timing behavior varies between designs. Treat the numbers as controls to test on that compressor, not as a universal preset for every instrument.
How do I hear attack?
Loop a drum passage in your DAW and set the compressor so you can hear gain reduction. Compare a fast attack with a slower one, matching the output level as you go.
A faster response can reduce more of the initial transient. A slower response may allow more of it through relative to the following sound. Neither is automatically better: controlling a sharp peak and emphasizing a drum's attack are different goals.
How do I hear release?
Keep the attack fixed and change the release. Listen for whether the gain recovers before the next hit or stays reduced through it.
A very short release can make level changes obvious or introduce distortion with some material. A long release can hold several events down together. You may want a noticeable rhythmic pumping effect, but first check that it is intentional and fits the song.
Compare compression fairly
- Name the problemChoose one passage and decide whether you want peak control, a steadier phrase or a different attack.
- Make the effect audibleSet threshold and ratio so the compressor responds on the relevant events.
- Adjust the timingCompare attack and release while listening to those events and the spaces between them.
- Match the outputBring processed and bypassed versions to similar listening loudness.
- Check the mixDecide whether the change helps the part alongside the other instruments.
When is automation more useful?
If one word or phrase needs to move forward, a deliberate level edit may solve it directly. Compression responds to its detector; it does not know which lyric matters most.
You can combine them. Adjust unusually quiet or loud phrases first, use compression for ongoing control, then automate a few musical moments afterward. The order depends on the result you want.
What is parallel compression?
Parallel compression blends a compressed signal with an uncompressed path. On drums, you might keep the clear original attacks while adding a more sustained processed layer underneath.
Set it up with a dry/wet control or a separate parallel route. Compare at similar loudness and check that routing or latency is not causing an unintended tonal change. Routing and Buses explains how parallel paths differ from inserts.
What does sidechain mean?
The sidechain is the signal path used to control the detector. It can use the processed track itself or another signal.
For example, a kick can trigger gain reduction on a bass track. The kick is the control signal; the bass is the sound being reduced. Adjust the amount and recovery so the bass movement serves the groove instead of vanishing unnecessarily.
Do I need compression on every track?
No. A well-controlled performance, a short sample or a sound already shaped by its envelope may need little additional control. Keep a compressor when it improves a specific relationship you can hear.
For the behavior of individual devices, consult their documentation. Routing and Buses shows where a compressor can sit in the signal path.