13 Free Mastering Plugins - Finish Your Music on a Budget

In this article, I’ll break down the top free mastering plugins. Mastering, the essential final stage in the production of a piece of music, includes sonic optimization of program material. Tools that mastering engineers use include equalizers, compressors, limiters, clippers, and much more. A lot goes into mastering beyond sonics, and it’s important for a mastering engineer to have quality monitoring, room acoustics, and a well-developed ear and understanding of musical genres. I recently completed a list of my own personal favorite mastering plugins, but for anyone on a limited budget who is just getting into the art and science of mastering, these free alternatives will surely serve as a great starting point.

1. iZotope OZONE 11 EQ

The Ozone 11 EQ, the latest equalizer plugin from iZotope, is designed to enhance any mix with its powerful and flexible features. As a standalone EQ plugin from iZotope’s renowned mastering suite, Ozone 11, it offers precise control and transparent sound quality for mastering engineers at all experience levels .

Key Features:

• Transient/Sustain Mode: This innovative mode allows you to shape the impact of your tracks by separately adjusting the transient and sustain components of your audio.
• Delta Button: The new Delta button lets you hear exactly how your adjustments are affecting the audio, making it easier to dial in the perfect curves.
• Mid/Side Mode: Shape your stereo image with precision using the Mid/Side mode, giving you control over the center and sides of your mix independently.
• User-Friendly Interface: The intuitive interface makes it easy to zero in on problem frequencies and make adjustments quickly and efficiently.
• Broad Compatibility: Ozone 11 EQ supports AAX, AU, and VST3 plugin formats, ensuring compatibility with a wide range of DAWs.

iZotope Ozone 11 EQ is a versatile and powerful equalizer plugin that brings innovative features and precise control to your mastering workflow. The Transient/Sustain mode, Delta button, and Mid/Side mode provide creative and technical tools that can significantly enhance your masters. With broad compatibility and a user-friendly interface, this free mastering plugin is a valuable addition to any producer’s toolkit, despite a few minor limitations. Whether you’re an experienced engineer or a budding producer, Ozone 11 EQ should be in your toolkit.

2. TDR Kotelnikov

TDR Kotelnikov is a sophisticated wideband dynamics processor designed to offer high-fidelity dynamic range control alongside exceptional musical flexibility. As a descendant of the esteemed TDR Feedback Compressor family, Kotelnikov incorporates several unique features, such as a proven control scheme, individual release control for peak and RMS content, an intuitive user interface, and advanced high-precision algorithms.Kotelnikov’s sonic footprint can be described as “stealthy,” allowing it to manipulate the dynamic range significantly while preserving the original tone, timbre, and punch of the musical signal. This makes it an excellent choice for stereo bus compression and even mastering.

Key Features:

• 64-bit Multi-Rate Processing Structure: Ensures the highest accuracy in dynamic range control.
• “Delta” Oversampled Signal Path: Maintains bit transparency at 0dB gain reduction.
• Super Fast, Natural Sounding Compression: Provides responsive yet smooth dynamic control.
• Crest Factor-Based Control Scheme: Offers independent release controls for peak and RMS events, enhancing flexibility.
• Flexible Sidechain Highpass Filter: Allows for precise frequency-dependent compression.
• Advanced Stereo Linking Options: Optimized for stereo bus applications, ensuring cohesive stereo imaging.
• Delta Preview Mode: Enables users to preview the difference between the compressed and original signals, aiding in fine-tuning.
• Latency Compensated, Click-Free Bypass: Ensures uninterrupted processing, even when bypassing the plugin.
• User Interface Rescaling: Offers rescaling options (100%, 125%, 150%) to fit various screen sizes and user preferences.

TDR Kotelnikov impresses with its user-friendly interface and intuitive control scheme. The plugin’s layout is clean and logical, allowing for quick adjustments and efficient workflow. The crest factor-based control scheme, which provides separate release controls for peak and RMS events, offers precise dynamic control and adaptability to different types of audio material.The flexible side-chain highpass filter and advanced stereo linking options enhance its utility for stereo bus compression, while the delta preview mode is an invaluable tool for detailed dynamic adjustments. Additionally, the latency-compensated, click-free bypass feature ensures seamless operation, making Kotelnikov a reliable choice for both mixing and mastering applications.

3. Voxengo SPAN

Voxengo SPAN is a highly-regarded audio analysis plugin. This real-time audio spectrum analyzer offers detailed and precise visual feedback, helping users fine-tune their mixes and master their tracks with confidence.

Key Features:

• Real-Time Spectrum Analysis: SPAN provides a real-time FFT spectrum analyzer, offering detailed insights into the frequency content of your audio.
• Customizable Settings: Users can tailor the spectrum display to their needs, adjusting parameters such as FFT size, overlap, and visual appearance.
• Multiple Channel Analysis: SPAN supports multi-channel analysis, allowing you to compare the frequency content of different tracks or monitor stereo channels separately.
• Free and Lightweight: As a freeware plugin, SPAN is accessible to all without compromising on quality or performance.

Voxengo SPAN is a powerful, versatile, and free mastering plugin for anyone involved in audio production. Its real-time spectrum analysis capabilities and customizable settings make it a top choice for both amateur and professional audio engineers. Despite a slight learning curve, the benefits it brings to your mixing and mastering processes are well worth the effort. Whether you’re fine-tuning a mix or mastering a track, SPAN provides the detailed feedback needed to achieve professional results.

4. Acustica Tan Compressor

The Acustica Tan compressor, offers a modern take on classic analog VCA compression. With its striking and simple graphical user interface and a versatile set of features, Tan stands out as a powerful tool for adding cohesion to masters.

Compressor Parameters:

• Threshold: Ranging from -64 dB to 0 dB, this allows for precise control over when compression kicks in.
• Ratio: Offers fixed settings of 2, 4, and 8, suitable for various compression needs from subtle leveling to heavy limiting.
• Attack: Adjustable from 0.1 ms to 30 ms, providing flexibility for fast or slow attack times.
• Release: Spanning from 0.1 sec. to 1.6 sec., enabling fine-tuned release settings.
• ShMod (Shape Modifier): A unique feature allowing the adjustment of the attack shape from 0 to 4. This control offers a novel way to tailor the compressor’s behavior to different audio sources.
• Gain: Adjustable from 0 dB to 24 dB, providing ample makeup gain to compensate for compression-induced level reduction.
• Dry/Wet: Facilitates parallel compression with a range from 0 to 100%, enabling blending of the compressed signal with the dry signal for more nuanced control.

Preamp Section:

• Hardware Preamp Simulation (PRE): This feature can be toggled on or off, adding an additional layer of analog-inspired warmth and character to your audio.

The graphical user interface of Tan is not only visually appealing but also user-friendly. The layout is intuitive, making it easy for both beginners and seasoned audio engineers to navigate and adjust settings. The inclusion of standard compressor parameters ensures that users can quickly dial in familiar settings, while the ShMod control adds a unique dimension to the plugin’s versatility.The Acustica Tan compressor is a robust and versatile tool that brings classic analog VCA compression into the modern digital domain. Its comprehensive set of controls, user-friendly interface, and innovative ShMod feature make it a standout plugin for anyone looking to enhance their audio productions. Whether you’re looking for subtle dynamic control or drastic compression effects, Tan has the flexibility to meet your needs.

5. Brainworx bx_masterdesk Classic

The Brainworx bx_masterdesk Classic is an entry-level version of their acclaimed all-in-one mastering plugin. Designed to provide a complete high-end analog mastering system in an easy-to-use format, bx_masterdesk Classic offers musicians, producers, and engineers the ability to achieve professional-quality masters with minimal effort and expertise, for no cost.

Key Features:

• High-End Analog Mastering Chain: The plugin emulates a curated chain of top-tier mastering gear, delivering the sound of a professional analog mastering setup.
• Simple 3-Step Workflow: With intuitive controls and clear metering, mastering is simplified into three main steps.
• Extensive Preset List: A variety of presets are available to provide immediate results and a great starting point.
• Onboard Stereo Enhancement and Saturation: Additional controls for stereo width and harmonic saturation enhance the mastering process.
• Tolerance Modeling Technology (TMT): Brainworx’s patent-registered technology adds a layer of analog authenticity by modeling component tolerances.

Three-Step Mastering Process:

1. Volume Control: Sets the overall level of the track as it hits the processing chain. The Dynamic Range VU meter helps in finding the perfect balance between loudness and quality.
2. Foundation Control: Adjusts the tonality of the master, allowing you to find the ideal balance between low and high frequencies.
3. Tone Control: Fine-tunes the overall vibe of your master, from bright to dark, ensuring that practically any setting will sound good.

For those looking to tweak further, the plugin also includes controls for Total Harmonic Distortion (THD) and stereo enhancement, allowing for added girth and width to the master. Overall, the bx_masterdesk Classic is an impressive free mastering plugin for those seeking an efficient and effective solution to finishing tracks. 

6. Brainworx bx_solo

Brainworx bx_solo is a versatile and powerful tool designed to introduce users to Mid/Side (M/S) recording, mixing, and mastering techniques. Better yet, it is available for free, providing an accessible entry point into M/S processing. With comprehensive solo features and a stereo width control, bx_solo offers essential functionalities for analyzing and enhancing stereo mixes.

Key Features:

• Solo Buttons for Detailed Monitoring: The plugin includes solo buttons for listening to the Left channel, Right channel, Mono sum (mid signal), and Stereo-Difference (side signal). This allows users to isolate and examine each component of a stereo mix, making it easier to identify and address issues.
• M/S Stereo Width Control: The stepped control lets users expand the stereo width of their tracks, adding depth and space to the mix. This feature is particularly useful on subgroups, FX returns, and stereo tracks like keyboards and guitars.
• Error Detection: bx_solo helps identify errors, noises, clicks, and other problems in your tracks or mixes, ensuring clean and professional results.
• User-Friendly Interface: The plugin includes fully automatable parameters and a “Mouse Over” feature for easy adjustments. Users can also type in exact values for precise control.

Brainworx bx_solo is another free mastering plugin for anyone interested in exploring M/S processing techniques. Its intuitive interface, powerful solo capabilities, and stereo width control make it a valuable addition to any audio toolkit. Whether you’re a beginner looking to learn about M/S processing or an experienced engineer needing a reliable error detection tool, bx_solo delivers high-quality results with minimal effort.

7. iZotope Audiolens

Audiolens is a groundbreaking desktop app from iZotope that revolutionizes track referencing and comparison. By analyzing audio from any streaming platform or audio source, Audiolens makes it easy to build a personal library of reference tracks that can be accessed anytime to compare against your own mixes or masters.

Key Features:

• Streamlined Track Referencing: Analyze audio from any streaming platform or audio source to collect data on key sonic characteristics.
• Personal Reference Library: Build a personal catalog of reference tracks, saving their tonal data to the Audiolens Target Library for easy access and comparison.
• Seamless Integration: Audiolens integrates effortlessly with Ozone 11 and Neutron 4, sharing your saved reference track tonal profiles with the AI Assistants in these plugins.
• Automatic Population: The app automatically populates saved reference targets to your Ozone 11 Target Library, allowing you to visualize and compare your master against chosen references.
• AI-Powered Assistance: Use the AI-powered Master Assistant to match the tone, dynamics, and width profiles of your reference track to your own master, with additional adjustments available through the Assistant View. 

How to Use Audiolens:

1. Analyze Audio: Play your chosen audio through the selected output of your device. Audiolens will collect data on key sonic characteristics.
2. Build Your Library: Save the tonal data of your references to the Audiolens Target Library, naming your tracks for easy retrieval.
3. Integrate with Ozone 11 or Neutron 4: If you own Ozone 11 or Neutron 4, Audiolens will share your reference track tonal profiles with these plugins, enabling seamless matching.
4. Match and Compare: Use the Master Assistant in Ozone 11 to match the tonal, dynamic, and width profiles of your reference track to your master, and fine-tune your adjustments in the Assistant View.

Audiolens by iZotope is a powerful and innovative tool for anyone serious about audio production. Its ability to analyze audio from any streaming platform or source, coupled with the ease of building a personal reference library, makes it an invaluable companion for mixing and mastering. When paired with Ozone 11 or Neutron 4, Audiolens enhances these plugins’ AI capabilities, making it easier than ever to match and compare tracks. Despite a slight learning curve, Audiolens offers tremendous benefits for achieving professional-sounding mixes and masters.

8. Acustica Jet

Acustica Jet is a dynamic EQ plugin bundle designed to deliver powerful and flexible audio processing capabilities. Positioned as one of Acustica’s flagship products, Jet combines high-quality sound with an intuitive design, making it a valuable tool for audio engineers who need to address mix issues quickly and efficiently. This suite includes the Jet and Jet Mix plugins, each tailored for specific mixing and bus purposes, and integrates both sampled and algorithmic EQs. That said, I wouldn’t hesitate to use Jet when mastering.

Key Features:

• Dynamic EQs Inspired by Elite Gear: Jet is influenced by top-tier bus compressors and features an updated design that offers a potent yet musical character.
• Hybrid Technology: Combines 50% analog emulation with 50% digital emulation, providing a balanced approach to dynamic equalization.
• Three Different EQ Models: Includes a sampled EQ with selected LF and HF band frequencies from the Eminence Acqua plugin and two algorithmic EQs (Digital Shelf and Digital Shelf HQ 2X) with an extensive range of frequencies.
• Dynamic and Static EQ: Offers both dynamic EQ capabilities for dynamic manipulation and static EQ for traditional spectral adjustments.
• 3 Modes of Operation: Classic Stereo (LR), Mid, or Side modes allow for versatile processing options.
• User-Friendly Interface: Resizable interface and intuitive controls ensure ease of use.
• Impeccable Sound Quality: Delivers a punchy and high-quality sound, with a powerful “glue” compressor for cohesive mixes.
• Internal and External Sidechain (SC): Enhances flexibility in processing.

Acustica Jet is a standout plugin bundle that offers a sophisticated approach to dynamic EQ processing. Whether you need to address mix issues on the fly or achieve a polished and professional master, Jet provides the versatility and power to get the job done without compromising on sound quality.

9. Youlean Loudness Meter

The Youlean Loudness Meter Free Version is a comprehensive tool designed to measure the true perceived loudness of audio. Known for its accuracy and reliability, this plugin is essential for anyone involved in audio production, ensuring that your mixes meet broadcast standards and sound their best across all platforms. With its user-friendly interface and extensive feature set, Youlean Loudness Meter offers everything you need for precise loudness measurements. I honestly use this tool on virtually every production. Go get it!

Key Features:

• TV and Film Presets: Supports various loudness standards including ITU-R BS.1770-4, EBU R128, EBU R128 S1, ATSC A/85, OP-59, ARIB TR-B32, AGCOM 219/09/CSP, ASWG-R001 HOME, and ASWG-R001 PORTABLE.
• Readouts: Provides detailed readouts including Loudness, Integrated Loudness, True Peak, Loudness Range, Dynamic Range, and Peak-Loudness Ratio.
• Graphical Displays: Features loudness and true peak histogram graphs, as well as a loudness distribution graph.
• Automatic Loudness Overdub: Supports automatic loudness overdub in timecode mode for precise adjustments.
• Flexible Interface: The resizable and scalable interface, including a mini view, ensures compatibility with any screen size, whether high DPI or not.
• Channel Support: Compatible with mono, stereo, and 5.1 audio content.
• Low CPU Consumption: Designed to be efficient, allowing for smooth operation even in complex projects.

The Youlean Loudness Meter Free Version is an outstanding tool for anyone needing precise and reliable loudness measurements. Its combination of accuracy, user-friendly design, and comprehensive feature set make it an invaluable asset for mastering.

10. D16 Group Frontier Self-Adaptive Limiter

Frontier by D16 Group is a self-adaptive limiter that is available free of charge to registered D16 software users. Designed to offer both simplicity and high performance, Frontier is an easy to use limiter that sounds fantastic. Whether you’re looking to control dynamics on a channel, bus, or master output, Frontier delivers excellent sound quality with a straightforward interface.

Key Features:

Control Input: Select the signal component used for controlling the limiter’s amplitude detection.

L|R: Maximum energy value of either the left or right stereo channels.

L: Energy value of the left stereo channel.

R: Energy value of the right stereo channel.

Mid: Energy value of the mid stereo component.

Release: Allows selection of one of three available AR envelopes for the limiter’s Voltage Controlled Amplifier (VCA):

• Fast: Slightly slow attack with fast release.
• Medium: Both attack and release set to medium time values.
• Slow: Fast attack with slow release time.

Threshold: Controls the threshold level below which the limiter activates its VCA and triggers the envelope.Reduction: The meter displays the current value of amplitude reduction introduced by the limiter.Output Level: Frontier features amplitude auto make-up, normalizing the output volume after limiting the signal. This knob controls the maximum amplitude value produced after normalization.Soft Clip: Enables a diode-like soft clipper that cuts out all peaks exceeding 0dB amplitude level.

11. Analog Obsession OAQ

Analog Obsession offers a wide range of fantastic plugins, available for free (though paying is an option.) The OAQ is a mastering grade EQ plugin, with an easy to understand interface, and fantastic sound quality.

Key Features:

• 6 band equalizer with selectable frequencies

• Low Cut (around 50Hz)

• DRIVE Control for Hefty Harmonic Saturation

• Mid/Side processing

• 4x Oversampling

Truthfully, given the quality and ease of use, I’m surprised the Analog Obsession plugins are free. A testament to the passion and talent of their designer, Rıdvan Küçük.

12. KClip Zero by Kazrog

Clipping is a useful tool for any mastering engineer needing to increase the perceived loudness of program material. KClip Zero by Kazrog is a powerful and versatile clipping plugin designed to provide transparent competitive loudness, total transient control, and a streamlined user experience. Featuring an advanced clipping algorithm modeled after their paid KClip 3, KClip Zero is an impressive free mastering plugin.

Key Features:

• Transparent Competitive Loudness: Gain extra headroom on your final mix or master without compromising sound quality.
• Total Transient Control: Tame harsh digital peaks to help your tracks sit better in the mix with less additional processing.
• Advanced Clipping Algorithm: The industry’s most powerful clipping algorithm ensures professional results.
• Mastering-Grade Oversampling: Offers up to 2x oversampling online and up to 16x offline for mastering-grade precision.
• Real-Time Visualizer: The new visualizer displays the amount of clipping in real-time, providing instant feedback.
• Resizable Window: The plugin window is resizable, allowing enhanced visualizer and metering to fit your preferred screen size.

13. MAnalyzer by MeldaProduction

MAnalyzer by MeldaProduction is a powerful spectral analyzer and sonogram plugin designed to provide detailed insights into your audio’s frequency content. With advanced features such as super-resolution, deharmonization, and magnitude normalization, MAnalyzer offers precise and versatile tools for mastering. 

Key Features:

• Spectral Analysis and Sonogram: Measures average, infinite average, temporary maximum, and infinite maximum for comprehensive audio analysis.
• Smoothing: Spreads energy between frequency ranges for better optical recognition.
• Prefiltering: Implements equal loudness contours, mimicking human hearing for more accurate analysis.
• Super-Resolution: Enhances resolution in low frequencies while maintaining speed in higher frequencies, overcoming limitations of standard FFT analyzers.
• Deharmonization: Reduces harmonics to isolate fundamental frequencies, aiding in identifying key frequencies.
• Magnitude Normalization: Provides better optical comparison by normalizing the magnitude of the spectrum.
• Freeze Mode: Allows you to freeze the analysis for detailed inspection.
• Copy/Paste to Clipboard: Facilitates comparison between different analyzer windows.
• FFT Sizes: Ranges from 1024 to 16384 for varying levels of detail and precision.
• Overlapping and Adjustable Windows: Ensures maximal precision in analysis.
• Global Preset Management: Allows saving and sharing settings across different projects and songs on the same computer.

Free Mastering Plugins Summary

While I still recommend that anyone serious about mastering invest in high-end plugins, software, monitors, acoustic treatment, and more, a lot of improvement can be made to your tracks by using these aforementioned free tools.