Plugin Alliance Audio Engineering Course: Part 3

Mastering Your Music for Distribution

Mastering is the final stage of the music production process. While mixing largely focuses on balancing individual instruments, mastering treats the entire stereo mix as one cohesive sound. Historically, mastering referred to the process of transferring audio to a physical medium, such as cutting grooves into a lacquer disc for vinyl distribution, recording onto magnetic tape, or preparing audio for compact discs. Each format came with its own technical considerations: vinyl required careful control of low-end and stereo width to prevent skipping, tape introduced gentle saturation and compression that shaped the sound, and CDs required precise level management to prevent digital clipping.

Today, mastering primarily focuses on optimizing and formatting songs for digital distribution, but the same fundamental goal remains unchanged. The purpose is to ensure the song's musical intention translates well across playback systems, whether that’s a phone, car stereo, studio monitors, club system, or festival rig. “Musical intention” simply refers to the emotional and stylistic character you want the listener to experience, including the balance, impact, and clarity that define how the song should feel from start to finish.

A high-quality master begins with creating a balanced mix on a neutral listening system (which can be achieved using headphone calibration, room correction, and hearing compensation software), so there’s minimal deviation across playback systems that hype lows, reduce mids, or emphasize highs.

You can achieve professional mastering results with just a few tools: an EQ, compressor, saturator, limiter, and metering plugin. Each serves a distinct purpose in shaping and optimizing a mix for distribution. All of the mastering plugins mentioned in this section of the course are included in the Plugin Alliance Subscription, which you can trial for free for 30 days.

1. Balance Tonal Character

The first step in mastering is to correct tonal imbalances that remain after mixing. If an issue affects only one instrument, fix it in the mix. Mastering is reserved for broad tonal adjustments that influence the entire song, not individual elements. For example, if the kick drum is too boomy, that’s a mixing issue; but if the entire track sounds muddy as a result of multiple sounds summing together, that’s a mastering concern. Even a great mix might have a little too much low-mid buildup or a slightly dull top end. A mastering EQ lets you shape a song's overall tone.

Mastering EQs differ from mixing EQs in both design and intent. Mixing EQs are often used to creatively sculpt or color individual sounds, while mastering EQs are designed for transparency and accuracy. Hardware mastering EQs achieve this through extremely low component tolerances, ensuring both channels behave identically and maintain perfect phase alignment across the stereo image. The AMEK EQ 200 carries this same level of precision into the digital world. Modeled after the earliest parametric equalizers of the 1970s and 1980s, it captures the clear, musical tone and smooth response that made those original designs studio staples.

Unlike a typical stock EQ that can sound clinical or sterile when making small adjustments, the AMEK EQ 200 combines analog warmth with detail and depth. Its design preserves the three-dimensional feel of the mix while helping you make sure corrections to balance and clarity. Each of its five overlapping bands offers broad, natural-sounding curves ideal for mastering moves such as trimming low-mid buildup or adding a touch of top-end air.

Before adding other effects, it’s common to use a mastering EQ to clean up undesirable characteristics like low-end rumble. You can also focus on balancing the mix at this stage, such as applying a gentle top-end boost to add polish and openness. Later in your processing chain, you may need to rebalance the mix with another EQ, and that’s okay.

2. Control Overall Dynamics

Once you’ve balanced the tone, the next step is to control dynamics so the mix feels smooth and consistent from start to finish. A mastering compressor adds cohesion, tightening the mix without flattening its energy. The Shadow Hills Mastering Compressor Class A is built for this purpose. Its Class A circuit modeling introduces subtle harmonic warmth while maintaining the transparency required for mastering.

For most genres, a gentle ratio of 1.5:1 to 2:1 provides natural, transparent control with mild gain reduction. More energetic styles, such as EDM or rock, can benefit from ratios up to 4:1 for a tighter, more compact sound. Generally, you’ll want to aim for around 1–3 dB of gain reduction to maintain clarity while smoothing peaks. Heavier compression can produce a more aggressive sound at the expense of dynamic range.

When mastering, there are two main types of compression you can apply: peak compression and glue compression. Each serves a distinct purpose and produces a different musical result.

Peak compression focuses on controlling energy build-up when multiple sounds sum together in the mix. Transient issues, such as overly sharp snare hits or kick attacks, should have already been addressed when mixing. In mastering, peak compression is used to smooth collective transients that push the mix too hard when layers combine. This creates a more consistent and controlled master. The effect is achieved with fast attack (0.1–10 milliseconds) and fast release (0.1–0.25 seconds) settings that react quickly to clamp down on peaks and then recover rapidly. The quick recovery prevents pumping effects on sustained material, keeping the compression applied transparent. This approach is a good choice when your master feels too “pointy,” “stabby,” or “loose.”

Glue compression focuses on general cohesion. It smooths the interaction between instruments, making the mix feel unified and natural. It helps all elements breathe together so the track feels musical rather than clinical.

With the Shadow Hills Mastering Compressor Class A, you can apply glue compression by using both built-in compressors together. Begin by engaging the Optical compressor (OPTICAL BYPASS set to “IN”), which naturally applies slower, smoother compression. Lower the Optical Threshold until you achieve 2–3 dB of gain reduction. Then engage the Discrete section (DISCRETE BYPASS set to “IN”) with a Ratio of 1.5:1 to 2:1, Attack around 0.1–10ms, and Recover around 0.25 seconds. Adjust the Discrete Threshold to add roughly 1 dB of additional gain reduction, just enough to gently reinforce the glue effect created by the optical stage.

Activate the Sidechain Filter (set to “IN”) to prevent the compressor from reacting too heavily to sub-bass content. Turning up the “HP SC FILTER” causes the compressor to become less reactive to low-end transients. This helps maintain punch and clarity in the low end while still controlling overall mix dynamics.

In most mastering chains, EQ comes before compression to remove problematic frequencies that might cause the compressor to overreact. A second EQ after compression can then fine-tune the tone, restoring brightness or reinforcing low-end weight.

3. Add Subtle Harmonic Energy

After balancing tone and dynamics, saturation can further tie a master together. A touch of harmonic enhancement adds richness to the mix, making it feel full without sounding distorted or over-processed. Tape machine saturation is often used for mastering because it enriches the sound, applies light compression, and smooths the top end. Combined, these effects can add depth and cohesion that traditional EQ and compression alone cannot achieve.

SPL Machine Head is designed for mastering-grade tape saturation and is an exact one-to-one match of the original digital hardware unit. Its saturation curve delivers the harmonic lift, dynamic tapering, and frequency-dependent compression associated with analog tape. It gives you flexible control over tape speed, low-frequency compensation, and high-frequency shaping, allowing you to match the saturation to the needs of the mix. Machine Head also effectively increases perceived loudness without raising peak levels.

Overdoing the saturation applied can quickly lead to unwanted distortion, so subtlety is key. Start with a low drive setting and listen for added depth, tighter low end, and smoother transients. Machine Head can introduce a slight shift in character, making the mix feel more solid and engaging, which is often desirable. If clarity begins to drop or the midrange starts to feel crowded, ease the drive back until the effect settles naturally into the mix. The goal is a controlled amount of saturation that adds fullness, presence, and perceived loudness while keeping the master balanced and clear.

4. Maximize Loudness

Once the tone, dynamics, and character are dialed in, a mastering limiter is used to maximize loudness and set the final output level. A limiter acts as an ultra-aggressive compressor, preventing peaks from exceeding the specified threshold level. If you were to simply turn up the volume of your mix, peaks in the signal would distort (“clip”) before you reach competitive loudness levels. A limiter applies gain reduction to these peaks while preserving clarity, letting you make your music loud without distortion.

Beyond increasing loudness, a limiter affects the density of a mix. Density refers to how solid, cohesive, and forward the audio feels once transient peaks are controlled and the average level is raised. As the limiter reduces sharp peaks, quieter details sit closer to the loudest elements, creating a tighter, more in-your-face sound. The mix begins to feel fuller because the dynamic gap between soft and loud elements narrows.

Some genres are mastered more densely than others. For example, EDM is often compressed much more than folk music. High-energy styles rely on a compact, upfront sound, so engineers use more limiting to achieve a steady, powerful level. Acoustic or dynamic genres benefit from greater contrast and space, so a limiter is used more gently to preserve natural transients. The goal is to match density to the musical style, keeping the master impactful without sacrificing the qualities that make the mix feel alive.

The Brainworx bx_limiter True Peak is designed for mastering. It prevents inter-sample peaks that can cause clipping on streaming platforms while maintaining stereo width and punch. Set the ceiling between -1.0 and -3.0 dBTP to account for headroom loss during transcoding to different codecs (more on this in the next section) and adjust the threshold until you achieve the desired loudness. Moderate limiting, usually around 1–3 dB of gain reduction, keeps the master clean and controlled. More aggressive genres may call for higher levels of gain reduction.

Pay close attention to how the limiter affects transients. If drums or vocals lose impact, increase the threshold level. Loudness should feel natural and effortless, not forced. The best masters maintain clarity, depth, and energy even at competitive playback levels.

5. Measure and Compare Results

The last step before export is to confirm that your master sounds balanced, competitive, and technically compliant with streaming requirements. A metering plugin ensures you’re hitting appropriate loudness and dynamic targets, while referencing lets you compare your track against other professional releases in the same genre.

ADPTR AUDIO's Metric AB streamlines this process by letting you instantly compare your mix to reference tracks. You can switch between your audio and multiple references with a single click and view side-by-side readouts for frequency balance, phase correlation, stereo width, dynamics, and loudness. Its loudness-matching feature ensures a fair comparison, so you can focus on tonal balance and overall dynamic character.

One of Metric AB’s more overlooked features is the filter section. You can solo sub, bass, low mid, mid, and high frequency content while swapping between your song and reference tracks. Mix imbalances become very apparent when comparing your mix at this level of granularity, so you may need to revise EQ adjustments earlier in your mastering chain if necessary.

6. Export Your Music for Streaming Services

Before delivering your master to a distributor, it helps to understand how streaming platforms handle audio. Services like Spotify, Apple Music, YouTube, and many others do not stream your lossless master file directly. Instead, they transcode it into a compressed audio codec such as AAC, MP3, Ogg Vorbis, or Opus. These codecs reduce file size for efficient streaming, but the conversion process can introduce problems like transient smearing, high-frequency artifacts, and even clipping if the original file has peaks too close to zero.

This means that a mix which sounds clean in your DAW may distort after the platform applies its own encoder. Because every service uses different codecs and bitrates, there is no single “safe” loudness or peak level that guarantees the master will translate perfectly everywhere. Transcoding can alter your waveform's shape and push peaks above your true peak ceiling, resulting in unwanted distortion during playback.

ADPTR AUDIO's Streamliner is built to solve this exact issue. It lets you preview how your music will sound after the major streaming platforms process it. You can audition codecs in real time, switch between AAC, MP3, Ogg Vorbis, and Opus, and hear how each streaming service’s specific encoding profile affects your audio. If a codec introduces clipping or artifacts, you’ll hear it immediately, allowing you to adjust your limiter settings before export.

Once you’re happy with your master, Streamliner can batch export compressed versions using each platform’s codecs. These exports are labeled automatically with codec and bitrate information, making it easy to test your mix on phones, laptops, car stereos, or any device your audience might use. Listening to these files will let you hear exactly what listeners hear via streaming services.

With everything optimized, you can export your final master for distribution. Export a 24-bit WAV file at 44.1 or 48 kHz and avoid normalization or dither unless you’re creating a 16-bit file for CD distribution. By pairing these standard delivery settings with a Streamliner-verified master, you significantly reduce the risk of distortion, artifacts, or quality loss when your music hits streaming services.

All of the plugins mentioned in this guide are included in the Plugin Alliance Subscription. It provides a complete mastering toolkit. Start a free 30-day trial to explore these plugins and process your music with commercial-quality mastering tools.