What helps smooth out aural soundscapes? Okay, so what makes a song sound like, well, a song? If you guessed audio compression, you're right.
Compression is essential and controversial. It's simple and complicated. And, most importantly, it's here to stay. Compression essentially helps adjust the dynamic range of a piece of music. It also helps clean up recorded unprocessed tracks before they're finalized. We know instrumentals and vocals can help shape a song. But a lot of music listeners miss one thing. Audio production processes like compression help 'iron out' the unprocessed recordings, which eventually make up the final track.
We previously learned about compression's essentials and the different compression equipment sound engineers use. But, you probably wonder, how does that come together? Let's take a moment and start learning, shall we?
A Quick Reminder about Compression
Compression, although supposedly misunderstood, is a powerful asset in music production. To recap, compression reduces the dynamic range of an audio signal's loudest and quietest parts. This process is achieved through lowering the loudest signals while boosting the quieter signals.
Sounds simple, right?
Compression is a little more complicated than that—especially when you get into using an actual compressor to work on your music. So, while you know you need to boost the quiet parts and minimize the loud parts, learning how to do so gets a little complicated… when you look at what you're going to use.
Fortunately, we're here to help explain.
How Compression Works in Audio Production
What does compression do for audio? Compression does a lot for unprocessed audio. It does so much for unprocessed audio many sound engineers and producers don't use it in the same way. In other words, everyone's got their own way to use compression for audio processing.
As mentioned in our last article, compressors reduce the dynamic range of an audio signal. The result: they make the loud parts quieter, smoothing out the playing field for the quieter and louder parts during playback.
Compressors are used in different ways. They can be used to clean up erratic sound dynamics. They can add more 'oomph' to a lacking instrumental. They help stitch together essential elements of a track. They introduce rhythm to lacking tracks. Some use compressors to change the tonality of different parts of a track.
Shaping Individual Sounds: The Effects of Compression
No matter how a compressor gets used, the result typically ends up different. The effects of compression vary based on how people uses a compressor. So, the most important thing to remember: compressors help even out the differences within an isolated track's notes. This produces a 'cleaner' track to use in a finalized song or musical piece.
Most of the time, compressors used on an isolated instrument recording can change how that particular instrumental takes shape. Isolated recordings, particularly for bass and guitar, can be 'cleaned up' and evened out. This produces a cleaner sound for the final cut of a song. The compressor becomes like an 'iron' – softening louder notes and broadening lower notes to produce a fuller sound.
It's the same for isolated vocals. Compressors help tame vocals otherwise uneven or accentuated in unprocessed audio. This helps produce a final version that could potentially work better in the final mix of a song.
Using A Compressor for Fuller Aural Works… With Purpose
What's the right way to use a compressor? Do most use compressors for cleaning up tracks? Evening out the sound fidelity? Or… perhaps something completely different? Fortunately, there's no right way to use a compressor. Sound engineers and producers all have their preferences.
But if you're starting out, you might need some guidance.
- Using a compressor to tame transients. A 'day to day' downward compressor using a fast attack-release time and high threshold allows you to tame transients in an audio track. Just to let you know, a transient is a short, high amplitude sound. A fast attack and release time enables the compressor to near instantaneously respond to the moment when the signal's amplitude hits the threshold. When this happens, gain reduction gets applied when the signal's amplitude rises above the threshold.
- Using a compressor to boost transients. Instead of reducing a signal's attack time amplitude, a compressor can reduce the signal's sustained amplitude. Here, the compressor is set to a medium attack time, synchronized release time and a high threshold. The threshold, in this scenario, can be set so the gain reduction only gets triggered by the track's transients. Attack time is usually increased to counter the gain reduction, allowing it to delay until the attack passed through the compressor. Delaying the gain reduction reduces the audio signal's sustained amplitude; it also allows gain reduction to continue until the next note starts. This technique is considered best for isolated instruments—bass, drums, piano, guitar and many others.
- Using a compressor for dynamic range reduction. Compressors naturally reduce an audio signal's dynamic range. By using a low threshold and ratio, a compressor can also expand an audio signal's dynamic range. The 'transient tamer' way of using a compressor involves setting the threshold to allow the compressor to only respond to an audio signal's transients. Another way to do this involves setting the threshold to allow the compressor to respond to the sustained and transient portions of an audio signal.
The inner workings of compression can't be covered in so little words, but the aforementioned purposes may give you an idea of where to start. But… how exactly do you approach audio compression anyway?
Using Compression: Effective Approaches for Aural Works
Compressors are used for two distinct purposes: to improve and to clean up tracks before compiling everything into a final mix. But there are two ways to approach this.
Approach 1: Instrument Compression
This approach involves ironing out individual isolated instrument tracks. You'd use a compressor to iron out imperfections and boost quiet parts of an instrumental track. Why?
It's simple. Every instrument used to make a song bears different nuances that might not work together in the final mix.
If you were to piece together your unprocessed parts, you'll have a very un-dynamic and messy sounding result. So, using compression is one part of the long sound production process that'll help clean up your tracks and make better sounding final mix. Compression helps bring out the best in each instrument, whether you need something punchier or fuller in sound.
Of course, getting into compressing individual tracks gets tricky. Everyone has their own way of approaching each instrument. You'll have to do a lot of testing to get a favorable result, bit it's pretty worth the effort.
Approach 2: Mix Compression
Compressing a near final mix gets tricky. At this point, the engineer's likely done compression for the individual instrumentals. Any more compression may end up squashing out the nuances of each track, producing a muddy and unpleasant sounding final mix.
So, how do you approach compressing a final mix? Some suggest using a compressor and limiter for mastering the final mix. Limiters handle the fastest transients, allowing the sound levels to be tweaked a little higher.
Extremely short or long attack times don't benefit the compressor in this case. Medium attack times control the signal level better, while allowing the percussion to shine through the mix. Release times should be shorter, however. Low ratios are also recommended, but avoid too much gain reduction.
Sure, compressors seem complicated—especially when you get your hands on one for the first time. Even though they have a complicated nature, they're ultimately used for one simple purpose: improving the quality of an audio track.
We hope our brief look at compressors cleaned up some curiosities about them. If you're interested in sound engineering, learning about compression is pretty important. Have fun testing it out when you get the chance!