Create Better Mixes: Compression in Music Explained

Compression in music is a fundamental technique that shapes the sound of your recordings and mixes. When you apply compression, you're manipulating the dynamic range of an audio signal—the difference in volume between the loudest and quietest parts of a track. 

Imagine listening to a vocalist who softly whispers one verse and belts out the chorus. The whisper would be too soft without compression, and the chorus might overwhelm. 

A compressor acts like an attentive sound engineer, turning down the volume when it gets too loud and bringing it up when it's too quiet, ensuring everything sits nicely in the mix.

Understanding how to use compression in music can truly elevate your production value. It balances levels and adds punch and presence to your sound. By controlling the dynamic extremes, compression helps individual elements blend smoothly, making it feel like everything was recorded under the same conditions. 

It's not just about preventing audio peaks; it's also about enhancing overall sonic cohesion, allowing each part of your music to be heard clearly and pleasantly.

Whether you're working on a dense mix or looking to control the dynamic range of a solo performance, compression is an indispensable tool. It's integral to mixing and mastering processes, helping you create a professional-sounding final product. 

Properly applied compression can bring out the nuances in your music, prevent distortion from a huge dynamic range, and give your audio a polished, consistent quality that listeners enjoy.

In Soundtrap’s online DAW, different compressors are available to control dynamics and make tracks sound more balanced and punchy. Sign up for free to try them out.

Fundamentals of Compression in Music

What Is Audio Compression?

Audio compression is the process of lessening the volume differences between the loudest and quietest parts of an audio signal. 

This process is achieved by using an audio compressor. The compressor automatically reduces the volume once it passes a certain threshold. 

Key parameters that you'll adjust on a compressor include:

• Threshold: The level above which compression starts

• Ratio: The degree to which audio that exceeds the threshold is reduced

• Attack: How quickly the compressor starts working after the threshold is exceeded

• Release: How quickly the compressor stops working after the audio falls below the threshold

• Make-up gain: Used to boost the signal after compression to balance the overall level

The Purpose of Compression in Music

Compression aims to create a more consistent level of loudness in a track and prevent unexpected jumps in volume, which can be unpleasant to the listener. 

Compression can also be used creatively to change the character of a sound or a mix. For example, a snappy compression setting can make a drum track feel more energetic.

Understanding Dynamic Range

The dynamic range of a track is the difference between its loudest and quietest parts, measured in decibels (dB). This range can be too wide without compression, making quiet parts difficult to hear or loud parts too overwhelming. 

Compressing the signal makes the dynamic range more manageable, ensuring all parts of the music are audible and impactful.

Types of Compressors

VCA Compressors

Voltage Controlled Amplifiers (VCA) compressors are known for their precision and versatility. They work well on various audio sources, offering fast attack and release times, which make them suitable for controlling fast transients. 

You'll often see them used on drums and in mix bus applications to tighten a mix without losing punch.

Optical Compressors

Optical compressors offer a smooth compression characteristic due to how they respond to incoming signals with a light-dependent resistor. They tend to have a slower attack and are favored for their musical and gentle compression, which works wonders on vocals and bass, helping these elements sit comfortably in the mix.

Tube Compressors

Tube compressors, or Variable-Mu compressors, utilize vacuum tube technology. They're cherished for their warm and rich tonal quality, which often adds a desirable character to the sound. 

A tube compressor will help your recordings gain not just level consistency but also a pleasing harmonic richness, making them a popular choice for busses and master tracks.

FET Compressors

Standing for Field Effect Transistor, FET compressors mimic the sound of classic tube compression but with faster attack times. They're the go-to when you want to add an aggressive edge to your sound, like brightening up vocals or giving drums more punch. 

Their distinctive 'bite' can excite a performance that needs to stand out.

Compression Parameters and Techniques

In music production, understanding how to manipulate compression parameters is crucial. It allows you to shape your sound with precision. Let's break down the core settings and advanced techniques to help you get the most out of this dynamic tool.

Setting Threshold and Ratio

Threshold

The Threshold is the level at which compression takes effect. You set the threshold to determine the point where the loud parts of your signal are reduced.

• How to set: Watch your track's metering and set the threshold below the peaks you want to compress.

Ratio

The Ratio determines the compression intensity applied once the threshold is exceeded.

• Examples:

  • A low ratio of 2:1 for gentle compression.

  • A high ratio of around 8:1 for more aggressive compression.

  • Anything over the ratio of 10:1 is considered limiting.

Attack and Release Times

Attack Time

The Attack controls how quickly the compressor reacts once the signal exceeds the threshold.

• Fast Attack Time: Use this when taming quick transients like snare hits.

• Slow Attack Time: Choose this for a more natural sound, allowing some transients through.

Release Time

The Release sets how soon the compression should stop after the signal falls below the threshold.

Adjusting Release: A shorter release time can help avoid a pumping sound, while a more extended release can provide a smoother feel.

Knee and Makeup Gain

Knee

• Soft Knee: Results in gradual compression, softening the transition into the compressed state.

• Hard Knee: Delivers immediate compression upon passing the threshold for more obvious control.

Makeup Gain

The Makeup Gain is used to compensate for the reduction in overall level caused by compression.

• Applying Makeup Gain: Carefully increase the output level to match the uncompressed signal's perceived loudness.

In Soundtrap you have three different compressors available for your productions - Compressor One and the Dynamics Compressor:

• Compressor One is a simple one-knob compressor where you just control the amount of compression applied. It's great for beginners with its easy-to-use one-control knob.

• Compressor Two is a two-knob compressor where you control the amount of compression applied and the range of compression.

• The Dynamics Compressor offers detailed controls for all the typical compressor parameters: Attack, Release, Ratio, Knee, and Threshold.

Advanced Methods

Parallel Compression

• Mix your uncompressed original signal with a compressed version for a more dynamic sound while controlling peaks. Parallel Compression is also often referred to as New York Compression.

Sidechain Compression

• Use sidechain compression to rhythmically duck the volume of other mix elements, for example, a bassline, whenever the kick drum hits.

Multiband Compression

• Split your signal into frequency bands using a multi-band compressor plug-in and apply different compression to each band.

Serial Compression

• Utilize multiple compressors in a series, each set for a specific task, often for more transparent control.

Handle these advanced techniques with care to avoid over-processing your mix.

Applying Compression in Mixing

Compression on Individual Tracks

When working with individual tracks, your goal is to control the dynamic range without squashing the life out of the performance. 

Use compression to smooth out levels and add consistency to each element.

• Vocals: Carefully adjust the threshold and ratio to ensure the vocal sits nicely in the mix without losing its natural dynamics.

• Guitars: Light to moderate compression can help tame erratic strumming or picking.

• Bass: Use compression to maintain a steady level, helping the bass to act as a solid foundation for the rest of the mix.

Tip: Always pay attention to the attack and release settings, as these significantly affect the sound character of the compressor.

Read more: How To Edit & Mix Your Vocals Online in 7 Steps

Treating the Entire Mix

Compression over the entire mix, or mix bus compression, can glue different elements together and create a cohesive sound. It's a subtle art that requires a gentle touch to prevent over-compression, which can make the mix sound lifeless.

• Threshold: Set this just enough to catch the peaks, generally without exceeding 2-3 dB of gain reduction.

• Ratio: A low ratio, like 2:1 or 1.5:1, is typically effective for mix bus compression.

Vocal and Drum Compression

Vocals and drums are the driving forces in many productions; hence, they often benefit the most from careful compression.

• Vocals: Aim for a transparent sound where the compressor reacts smoothly, maintaining intelligibility and presence in the mix.

• Kick Drum: Achieve punch and tightness by using a medium attack and a quick release, allowing the kick to cut through the mix.

• Snare Drum: A faster attack can tame transients, while a slower one can increase the body and 'thwack' of the snare.

Use solo and bypass functions frequently to compare the processed and unprocessed signals as you apply compression. This helps you maintain a frame of reference and ensures you're enhancing, not degrading, the quality of the track.

Balancing Levels and Gluing Tracks

When individual elements in your mix have huge dynamic ranges, compression helps to balance those levels, making the quiet parts more audible and the louder parts less overpowering. 

This form of transparent compression is often subtle—as if it's not even there—yet it works tirelessly to ensure every note you play sits nicely in the overall mix.

Common Uses

• Taming peaks on vocal tracks

• Evening out the performances of bass and guitar

• Controlling the transient hits of a snare or kick

When applied to a mix bus, subtle compression can help the different elements of a track feel as if they belong to the same sonic world, resulting in a more cohesive, "glued" sound.

By crafting the right amount of compression, your mix can go from good to great. Remember, it's not just about the overall level; it’s about finding that sweet spot where your compression sounds expressive and intentional.

Conclusion

Mastering the art of compression in music production is paramount for achieving professional and polished mixes.

Whether working on individual tracks or applying compression to the entire mix, the goal is to maintain a consistent level of loudness while preserving the natural dynamics of each element. 

Different types of compressors, such as VCA, optical, tube, and FET compressors, offer versatile options for creative and precise compression.

Understanding advanced techniques like parallel, sidechain, multiband, and serial compression empowers music producers to tailor their sound with finesse. Whether taming peaks on vocal tracks, balancing guitar performances, or controlling transient hits on drums, compression proves to be an indispensable tool in achieving a cohesive and expressive mix.

Compression is not merely a technical process but an art form that elevates the listening experience by ensuring clarity, balance, and impact. 

With a clear understanding of compression fundamentals and careful application of techniques, you can take your mixes from good to great.

About the author

Tero Potila is a professional music composer and producer. His career combining knowledge and experience from music, TV, film, ad, and game industries gives him a unique perspective that he shares through posts on teropotila.com.