Plugin Alliance Audio Engineering Course: Part 2
Identifying and Correcting Mix Issues
Mixing music is like solving a puzzle. Each sound is a piece that needs to fit perfectly with the others to form a clear and balanced picture. When something doesn’t sound right, your job is to identify the problem, isolate it, and make adjustments until the issue is resolved. The process is complete once every element sits naturally in the mix and nothing stands out for the wrong reasons. At that point, your mix is technically finished, and any further tweaks become creative choices rather than corrections.
The good news is that 90% of mix issues can be fixed with just six tools: an EQ, compressor, saturator, reverb, delay, and pitch correction plugin. While Plugin Alliance has a massive catalog of mixing plugins, this section of the course will focus on a handful of highly versatile mixing plugins to help get you started.
All of the plugins mentioned in this guide are included in the Plugin Alliance Subscription. Start a free 30-day trial to experiment with these mixing plugins yourself.
1. Fixing Frequency Imbalance
Frequency imbalance is one of the most common mix problems. Too much low end makes a mix muddy, harsh mids make it fatiguing, and weak highs make it dull. The goal is to create balance so each instrument has its own space and the mix sounds clear and natural.
Three-Body Technology’s Kirchhoff-EQ is a modern mixing EQ that can be used on all your tracks. It has 32 bands and 15 filter types (analog and digital) that let you clean up rumble, reduce harshness, and add clarity. For more detailed control, it provides dynamic bands that only react when frequency buildup occurs, helping you transparently control resonance and avoid frequency masking.
An EQ is the one mixing plugin you’ll use the most because it can solve a wide range of character-related issues. Drums too “thumpy?” Use an EQ. Vocals not “airy” enough? Use an EQ. When you’re trying to add or remove a particular tonal characteristic from a sound, an EQ is often the answer.
EQs come in different flavors, each offering a distinct tone and workflow. Some are designed for transparency and precision, while others add warmth inspired by vintage hardware; the Kirchhoff-EQ just happens to provide both.
2. Controlling Uneven Dynamics
When track levels fluctuate too much over time, elements can jump out of the mix and draw unwanted attention. For example, an overly dynamic acoustic guitar may overpower a delicate vocal at various points in time if its levels are not adequately controlled. Properly managing dynamics lets you set tighter track levels and create mixes that feel glued together and cohesive.
In the days of analog tape recording, before digital audio workstations (DAWs) became standard, recording engineers often “rode” the faders on mixing consoles in real time. This allowed them to manually control and record volume changes directly to tape, embedding those dynamic adjustments into the performance itself. Automating a track’s volume envelope in your DAW serves the same purpose today, but it’s still not the most efficient or musical way to control dynamics.
The Three-Body Technology Cenozoix Compressor is a plugin that controls the dynamic range of sounds. It does that by lowering the volume when sounds get too loud. If a vocalist sings “For you I have so MANY words,” you can use the Cenozoix Compressor to reduce the level of “MANY,” to create “For you I have so many words.”
The way gain reduction is applied significantly impacts the resulting sound. You need to tell the compressor when and how it should apply gain reduction based on the incoming audio signal. You do this by adjusting its controls:
- Threshold: The level at which gain reduction is applied to the signal.
- Ratio: The intensity of gain reduction applied when the signal jumps above the threshold level.
- Attack: The time it takes for a full dose of gain reduction to be applied when the signal jumps above the threshold level.
- Release: The time it takes for gain reduction to stop being applied when the signal drops below the threshold level.
Not all compressors are created equal. Some have inherently fast attack and release settings, while others behave slowly. Certain compressors add distortion that sounds great for metal vocals, electric guitars, and drums, while others add rich, sweet-sounding harmonics suitable for folk vocals and acoustic instruments. In the world of hardware compressors, these differences can be quite extreme due to variations in circuit design, such as the use of tubes, transistors, optical cells, or voltage-controlled amplifiers, each imparting its own unique tone, response, and character to the signal.
Compressor plugins designed based on the circuitry of hardware compressors are called analog-modeled compressors. Accurately modeling analog equipment is what Plugin Alliance is best known for. While analog-modeled compressors are extremely desirable for their unique characteristics and variety of flavors, the sheer number of options can make choosing your first analog-modeled compressor a challenge.
Three-Body Technology’s Cenozoix Compressor is an ultra-versatile option that provides the sound of 12 classic compressors. With algorithms like “Black FET,” “Blue FET,” “Vintage Opto,” and “Virtual-Mu” packed into a sleek UI, and with all the features you’d expect from a modern compressor plugin, the Cenozoix Compressor is a great way to kickstart your analog-modeled compressor library.
3. Fixing a Flat or Lifeless Mix
Even if your mix is balanced with EQ and compression, it can still sound dull or two-dimensional. This often happens when recordings are too clean and lack the subtle harmonics that give professional mixes a full, dense sound. Without those layers of harmonic content, instruments can feel disconnected, leaving the mix feeling emotionally deflated.
Louder Than Liftoff’s SILVER BULLET mk2 solves this by adding the kind of analog warmth and movement that digital recordings often miss. It uses three analog-style “MOJO” amp circuits, each providing different flavors of saturation, ranging from smooth and polished to bold and gritty. By blending these harmonics across your tracks or mix bus, you can introduce depth, presence, and perceived loudness without losing clarity.
Beyond simple saturation, SILVER BULLET mk2’s DYNA REALISM™ and ASPECT RATIO features bring your mix to life with subtle variations and stereo enhancement, mimicking how real analog hardware behaves. With just a touch of drive, your mix can go from sterile to vibrant, becoming rich, dynamic, and emotionally engaging.
4. Creating Depth and Space
A mix without depth can sound crowded, like all the instruments are stacked on top of each other. Reverb helps correct this by simulating natural space, giving every sound its own position in the stereo field. Increasing the amount of reverb applied to a sound can push it to the back of the mix, making it sound farther away. This can enhance the realism of the soundstage and separate sounds in crowded mixes.
When a mix sounds flat or boxy, it usually means everything is sitting in the same space. Vocals fight with guitars, drums feel glued to the front of the stereo field, and the whole mix lacks separation. Brainworx’s bx_aura reverb fixes this by letting you shape depth and dimension using five unique reverb algorithms. “Room” creates realistic early reflections that make instruments feel naturally placed in a physical space. “Space” delivers a wide, lush reverb with subtle motion, helping the mix feel open and immersive. “Soft” smooths out transients and reflections for a gentle, pad-like effect that glues sounds together without blurring details.
For more creative mixing, “Echoes” adds rhythmic reflections that sit between a delay and a reverb, helping create motion and depth without overpowering the dry signal. “Reverse” produces swelling tails that rise before fading naturally, perfect for transitions or adding drama to sustained sounds. You can add diffusion to both algorithms for a smoother, more immersive texture. bx_aura makes it easy to open up a mix, carve out space for every element, and create the stereo field depth that separates a beginner mix from a professional one.
5. Correcting Timing and Movement
While reverb creates the illusion of space by diffusing sound, delays do this through rhythm and repetition. Instead of washing a signal into the background, a delay adds defined echoes that create space and movement without reducing clarity. Delays can lock sounds to a song's groove, reinforce timing, and make instruments feel more in sync with the track's rhythm. A mix without delays can sound static, lacking pulse and forward motion.
Brainworx’s bx_pulsar is a versatile delay plugin built for precision and creativity. It includes five core delay modes that span from clean digital repeats to warm analog echoes to modern sound-design textures. “Air” provides crisp, transparent delays that blend smoothly into a mix. “Magnetic” adds a tape-style echo character, from hi-fi reel-to-reel to dusty cassette tones. “Circuit” captures the imperfections of vintage analog hardware for gritty, modulated repeats that add movement and color. “Aether” delivers experimental soundscapes with pitch-shifted, grain-based effects, and “Reverse” creates backward delays that swell and fade for dramatic rhythmic impact.
bx_pulsar lets you shape groove and space. Its eight-step sequencer lets you pan individual echoes across the stereo field. Built-in ducking and swing controls make it easy to keep echoes in sync with the track while staying out of the way of the main performance. With bx_pulsar, you can turn static parts into rhythmic elements that breathe with the music and give your mix a stronger sense of motion.
6. Correcting Pitch and Tuning
Even a well-balanced mix can sound unpolished if there are pitch issues. Slightly off-key vocals or instruments can draw attention away from the music and make the entire mix feel less confident. Pitch correction helps tighten performances so every note fits the key of the song, keeping the listener focused on the emotion rather than the imperfections. The goal is to correct pitch while maintaining a natural, expressive performance.
Brainworx’s bx_crispytuner is designed to make this process fast, transparent, and musical. It can automatically correct small pitch variations or allow precise manual adjustments for more detailed control. Its real-time visual feedback makes it easy to spot inconsistencies, and the correction strength can be tailored to suit the material, from subtle natural tuning to more stylized vocal effects.
When a performance sounds slightly off, bx_crispytuner helps bring everything back into tune. It aligns vocals and instruments to the song’s key so melodies and harmonies sit naturally together. By fixing small tuning problems, bx_crispytuner helps the mix sound cohesive and polished without sacrificing the character of the performance.
bx_crispytuner can also be used as a creative tool instead of just a corrective one. Increasing the tuning strength to "Extreme" produces the robotic, T-Pain-style vocal sound often used in pop, hip-hop, and electronic music. Combining this effect with harmonies or stacked vocal layers can create unique textures that stand out in a mix, turning pitch correction into a powerful element of artistic expression.
Finishing Touches and Advanced Tools
The six tools covered in this guide will handle about 90% of the problems you’ll encounter in a mix. The remaining 10% calls for more specialized tools, such as de-essers for controlling vocal harshness, transient shapers for tightening drums and percussion, stereo imagers for adjusting width, and gates for cleaning up noise between phrases or tightening multi-mic recordings. These plugins are used to address more specific issues that arise after the main problems have been corrected.
All of these tools, along with the plugins featured in this guide, are included in the Plugin Alliance Subscription. It provides access to a complete collection of mixing plugins from the world’s top plugin developers, giving you everything you need to identify and fix mix issues. Start a free 30-day subscription trial to explore the complete Plugin Alliance catalog.