Plugins and Processing: Understanding EQ, Compression, and the Tools That Shape Your Sound

Equalizers change volume of different frequencies.

Filters 'cut off' certain frequencies, letting other sounds pass by. A high-pass filter will cut off low frequencies and let the higher frequencies pass by so you can hear them. A low-pass filter does the opposite, cutting off the high frequencies and letting the lower frequencies pass by.

Music creators use EQs and filters to shape tone, remove mud, brighten vocals, and carve space for instruments.

Compressors control the dynamic range of sound passing through them. But what does that really mean?

Dynamic range is the volume difference between the loudest and quietest parts of the song.

Compressors 'compress' that range. Typically, that means hearing more of the quiet parts of a track. However, compressors can be configured to smooth or create 'punch' in a track.

Saturation is a form of distortion. It focuses on adding harmonic content to a sound.

Harmonics are how our ears tell the difference between different natural sounds, like a trumpet playing the same note as a violin.

Saturation is also used to 'thicken' sounds or creating a 'warmer' feeling. It also can create a more 'dimensional' sound when used appropriately.

At a base level, these plugins add echoes to your sound. Delay plugins tend to add very specific repetitions of the original source sound. Reverb plugins tend to sound like the reflections coming from a room's walls or other solid surfaces.

These tools are used to create a sense of depth in a song. They fall under the spatial processing category.

Not everything in the land of plugins will be about shaping sound. Meters, analyzers and gain plugins help you understand what’s happening in your song.

I use meters all the time to help me along the music creation process - when you measure, you know where you are sitting.

EQ (equalization) is one of the most essential tools in music production. It shapes the tone of every sound, removes unwanted frequencies, creates space between instruments, and helps your mix feel clear instead of crowded.

While compression controls dynamics, EQ controls frequency balance - the foundation of how your music actually sounds.

Have you ever heard a sound and it just did not sit right with your ears? Or maybe a guitar was fighting with the vocals? Well that is typically when we would reach for an EQ.

Every sound occupies a range of frequencies. When those ranges overlap too much, your mix becomes muddy, harsh, or unfocused.

EQ helps you:

EQ is both corrective and creative. It can fix issues, but it can also shape a sound into something new.

You might find that a vocal recording has some unpleasant resonance that pokes at your ears - you can use EQ to help tame that.

And what about the kick drum that just doesn't have enough oomph - you can use EQ to help boost the low end and shape that sound.

There are multiple types of EQs. Although all of them work to change the volume of a specific frequency, they operate a little differently in their mechanics:

Parametric EQs are really helpful for problem‑solving. Analog‑modeled EQs are ideal for tone‑shaping and adding bonus saturation. Dynamic EQs are ideal for controlling frequencies that change over time.

EQs become powerful when you use them with intention. Think about these things before you make your moves:

EQing is not about making every sound perfect - especially when soloing tracks. Rather, it is about helping each sound to fit together nicely.

Because there isn't a place where EQing could not be used, it means being extra careful with your adjustments. Pay attention to these use cases:

EQs are one of the few tools that can appear in almost any of the stages of music production. But use it with clear intent and your songs will be better off.

Saturation is one of the most misunderstood tools in music production. It’s not just “distortion” - it’s harmonic enhancement. When you add saturation, you’re adding new frequencies that weren’t originally in the signal, especially in the higher frequencies. These harmonics make sounds feel fuller, warmer, and more present.

Recording today is primarily done with digital audio. Digital audio is clean - sometimes too clean.

Saturation adds the "imperfections" that make music feel alive. If you have ever heard a song that had that warm 'analog feel,' that happened because of saturation.

Saturation can:

Just as there are different types of EQs, there are different types of saturation. The importance here is not to memorize each one, but rather understand the kind of feel that each provides, as each one adds its own flavor.

So, where exactly would you use saturation? Here are some of the common areas where you might want to reach for a saturation plugin:

Remember that the key here is a subtle response - not something that creates obvious distortion, heavy fuzz, or a 'wooly' sound. When you apply saturation, turn up the knob too far and then dial it back to where it sounds best.

Did you know it is possible to see what harmonic content a plugin is adding to your sound? That's right. With a utility tool like Melda's MMultiAnalyzer, you can visualize the harmonics a plugin generates.

This helps you understand what the plugin is actually doing - not just what it sounds like. And if you want to know how to do this, you can check out the Embervane Test Tone Files, a free set of test tones with instructions on how to see harmonics and more.

Compression controls the dynamic range of sound - the difference between loudest and quietest parts. It shapes transients, smooths performances, and helps instruments sit properly in the mix.

But not all compressors are the same. They have different 'personalities.'

After saturation, I feel that compression is one of the most misunderstood aspects of working with music. Sure, people can get a handle for what it does, but to truly be able to understand how to make a compressor dance for you is something else.

Just like EQs, compressors have both technical and creative sides. But for now, we start with the core concepts. Compression can help you:

Different compressors will sound different. Why? Because different compressors used different methods of controlling the dynamic range - I'm talking at the electronics level.

And those decisions lead to different sounding compressors. Take this overview as an example:

Don't fall into the trap thinking that one compressor type only works with one purpose - that is not true. For now, keep things simple and just understand that these different sounds or feelings are what you should keep your ears open for.

Then, you can make better decisions later about which compressor you reach for on a specific track.

As long as you remember that these rules are not hard and fast, then consider some rules of thumb for your compressor choices:

If you are using compressors, especially on a bus, it actually makes sense to calibrate those compressors first. And yes, even when using plugins.

If you have set your mixing levels correctly, you can control the amount of compression that is happening at the bus level.

How do you do that? By using a 1 kHz sine wave at -18 dBFS RMS, conveniently provided as part of the Embervane Test Tone Files free resource. You even get specific instructions showing how to calibrate a bus compressor.

Reverb creates space. It tells the listener where the sound “lives.” This is how we position a sound on a virtual soundstage for the listener.

Are we listening in a small jazz club with an intimate vocal? Are we in a concert hall with a full orchestra? How about a rock room?

Different reverb types create different spatial effects, which trigger different emotional responses.

A plate reverb uses a literal plate of metal. Sound is broadcast against it on one end and a microphone picks up the delayed vibrations on the other end.

It can sound bright, smooth, metallic. It can work with vocals, snares, and melodic instruments.

A hall reverb simulates the kind of lush and long echo tails that come from large spaces, namely a concert hall. This kind of reverb is really powerful, but can also quickly overtake the other sounds in your song - use with caution.

It can sound cinematic and rich. It is great for pads, strings, and ambient music.

While a hall reverb is very large, a room reverb tends to be smaller, yet still captures the reflections off of the walls of the space.

It can sound smaller, natural, and intimate. It can work well on drums, guitars, and realistic smaller spaces.

Nothing else quite gives the sense of a room that the instruments are playing in like reverb. It is incredibly powerful, when used correctly, to create an immersive listening experience even with stereo speakers.

Reverb helps you to:

When choosing which reverb to use, know that there are accurate reverbs and stylistic reverbs. Accurate reverbs will model a room as if you were in it - this can be really strong for creating a sense of cohesive space.

Stylistic reverbs can add a flavor to the sound that may be desirable.

Think about what you are trying to achieve when using reverb. It is so easy to overdo it here, so start small and work with intent.

Here are some quick guidelines for reverbs that may work well with different instrument types:

At its core, a delay is an echo tool. By controlling how long the echo is heard, how fast it bounces back, how fast it decays away and where we hear those bounces, you can increase the musical expression of a track.

Delay adds movement, rhythm, and texture. It’s more than just an echo - it’s a creative tool that shapes the feel of a track.

Here are some examples of what delay can do in your music:

Delay can replace reverb when you want space without wash: short delays add presence - long delays add drama.

But, just like reverb, this kind of thing is easy to overdo. Why? Because the spatial effects (reverb and delay) sound cool but also compete with the main sound.

If we hear the spatial effects at too loud of a level, our brains lose interest in the main sounds. And that would be like zoning out to the echoes at a concert instead of focusing on the performance!

On some plugins, you will see an option to use oversampling. Typically, this will have some kind of multiplier like 1x, 2x, and so on.

Oversampling increases the internal sample rate of a plugin so it can process audio more accurately. This reduces aliasing - unwanted digital artifacts that appear when harmonics exceed the Nyquist limit.

And that is a whole bunch of technical talk that means this: If you are getting some unpleasant distortion or frequency responses when using a plugin, try bumping up the oversampling to see if it goes away.

Why not use oversampling all the time? Because oversampling means more work for the CPU and that kind of thing adds up.