Microdynamics in Mixing (Part 2): Compression, Sidechain and Automation: Advanced Dynamic Mixing Techniques
Bus Compression and Mix Glue
Dynamic processing can be applied not only to individual tracks, but also to groups of instruments.
This is known as bus processing.
Common examples include:
drum buses
backing vocal buses
guitar buses
synth groups
Bus compression is often used to create a sense of cohesion between multiple tracks.
Rather than sounding like isolated recordings, instruments begin to feel like they belong to the same performance.
In many mixes this compression is subtle and works alongside the individual processing applied to each track.
However, excessive bus compression can sometimes mask underlying mix issues, so it should be used carefully.
Tip
Use bus compression primarily to create cohesion rather than to solve major mix problems.
Automation and Dynamic Control
Automation is one of the most powerful tools for shaping microdynamics.
While compressors perform most of the dynamic work automatically, automation allows extremely precise control over specific moments in a track.
Historically, engineers performed these adjustments directly on mixing consoles using manual fader moves, often referred to as fader rides.
This technique is still widely used today, particularly for:
lead vocals
melodic instruments
solos
Performing level adjustments in real time often produces more natural musical results than drawing automation curves with a mouse.
Sidechain Compression
A dynamics processor normally uses the input signal itself to trigger compression.
Sidechain processing allows a different signal to trigger the compression instead.
Although sidechain compression is commonly associated with the pumping effect used in electronic music, it also has many subtle and practical mixing applications.
One of the most useful is reducing frequency masking between instruments.
For example:
bass can briefly dip when the kick drum hits
background instruments can duck under a vocal
pads can move out of the way of melodic elements
This allows important sounds to remain clear without permanently lowering the level of other tracks.
Serial Compression
Complex sources such as vocals often require several forms of dynamic control.
A vocal performance might contain:
transient consonants that affect intelligibility
sustained vowels that define tonal body
peaks within phrases
large level changes across different sections of a song
Attempting to control all of these elements with a single compressor can produce unnatural results.
Instead, engineers often use serial compression, where multiple compressors perform smaller, targeted adjustments.
For example:
a fast compressor to control peaks
a slower compressor to shape overall dynamics
additional processing such as EQ or saturation
This approach generally produces more transparent and predictable control.
Next in the Series
Future articles will explore additional advanced dynamic techniques including:
parallel compression
frequency-selective compression (de-essing)
expansion strategies
transient shaping
gating and limiting
dynamics and tempo relationships
If you're interested in learning these techniques in depth, I offer one-to-one music production and mixing lessons at my Berlin studio.
