Everything you need to know about iZotope RXRX is an audio restoration toolset whose seeds were sown in 2003 with a research project that resulted in three innovative tools: De-click, De-clip and Spectral De-noise. It was 2007, however, when those tools were bundled with a suite of more conventional audio processors and a powerful spectral audio editor, and released to the world as RX.
We’re used to working with audio in the time domain, but by adding access to the frequency domain spectral editors make it possible to fix audio glitches and problems in ways that are impossible with purely time-domain processing.

READ MORE: Review: iZotope RX 12’s focus on improved accuracy and quality pays off

As a result, it’s no big surprise that RX was a big hit in industries where being able to make a quick repair could save hundreds – if not thousands – in re-shooting, re-recording, and/or re-mixing costs. We’re talking TV and film post-production facilities, along with a bit of audio mastering, but there was less initial interest from music producers.
This started to change with the 2017 release RX 6, the first version of the software to harness the power of machine learning (ML) to enable functionality that seemed to border on the magical.
Machine Learning Meets Audio Editing
Image: Press
ML works by being trained to recognise patterns. Initially recognition is very poor, but over thousands of rounds of training, and refinement of the resulting neural networks, it becomes more and more able to recognise different types of sound. From here, it’s relatively straightforward to create algorithms targeted at the frequencies that constitute a given type of sound, be it to attenuate that sound, such as for noise reduction/removal, or to lift it out of the audio entirely, such as with stem separation.
In RX’s case musical stem separation is handled by the Music Rebalance module, which allows in-place volume adjustment of vocal, drums, bass and “other” stems (a godsend for mastering engineers!), or can separate those stems entirely. Two similar tools are aimed at TV and film production, namely Dialogue Isolate that removes background noise from dialogue, and the new Scene Rebalance that operates similarly to Music Rebalance but recognises dialogue, music and effects.
Working with separated stems in RX 12 has been massively improved thanks to the new Stems View which allows you to work with separated stems as lanes within a single window. I talk more about this excellent new feature in my review.
Not all of RX’s tools use ML, but the vast majority do in some form or other, and iZotope are steadily working through those that don’t, adding ML where there’s some advantage in doing so. For example, in RX 12, the De-bleed and Breath Control modules are the latest to receive an ML-based overhaul, making them both quicker to deploy and more accurate in their results (see my review for more about this).
Will RX Be Useful For Me?
Scene Rebalance in iZotope RX 12. Image: Adam Crute
Although capable of straightforward editing and processing – cut/copy/paste operations, gain and EQ adjustment, and such – RX’s main focus is on restoring damaged and poor quality audio, with a side-order of enhancement tools that can add polish in ways other plugins cannot. A good example of the latter would be using Music Rebalance’s stem splitting during mastering to tame an overly-dynamic drum stem without impacting the rest of the mix.
It is in restoring audio that RX is truly at its best, however, and it’s easy to see the value of being able to rescue a take or performance that’s perfect but for the squeaking of a piano pedal, the occasional mic pop, or the performer delivering an unexpected spike in volume that causes some clipping? Also invaluable is the ability to repair glitches that you didn’t notice during a recording session, and long after the performer(s) have gone off to do whatever-it-is they do while we’re topping-up our studio tans!
The newly-released RX 12 brings enhancements and improvements that only add to these restorative abilities. The ML-based modules benefit from increased accuracy and transparency thanks to iZotope’s focus on improving its models through countless rounds of training (using ethically sourced and properly licensed training material). The ML algorithms run more efficiently too, so the improved results are delivered with less hanging-around than before.
So, if you work in a studio with faultless equipment and perfect noise isolation, RX may be surplus to requirements, but if you work in a studio in the real world then there’s no doubt it will come in useful.
What Do I Get With RX?
De-bleed in iZotope RX 12. Image: Adam Crute
RX comes in three editions aimed at different types of user. Elements is for those who may need fix common audio problems such as clicks, pops, and overly-reverberant signals, but have no need for a full-features spectral editor. As such, the package comprises a set of plugins for loading into your DAW, but no standalone RX editor software.
Standard edition does include the spectral editor along with all of the restoration and enhancement tools you’re likely to need in a music production context. All of these are available as modules within RX, and many also have realtime plugin counterparts for use in your DAW, including Music Rebalance, Spectral De-noise, De-plosive, and Breath Control.
Advanced edition includes everything found in Standard along with some very attractive and powerful nuggets such as EQ Match, Ambience Match, Spectral Recovery, and Scene Rebalance. If you often work with audio for visual media then these tools will likely prove exceptionally useful (although the price may make you wince!), but for everyone else it’s unlikely the Advanced-only modules and plugins will prove useful.
A full list of the modules and plugins included in each edition of RX, along with explanations as to their functions, can be found on iZotope’s website, as can pricing details and upgrade options. Also, be sure to check out my review to find out more about RX 12’s new abilities features.
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