I have included a number of basic spectral editors, as well as applications which include spectral editing capabilities, in the TOOLS listings of this website since they are a good starting point for familiarizing oneself with the spectral content of one's source material and can be useful for experimenting with spectral editing. In some cases they are even available for free! Depending upon the source material, one might be surprised by what is possible using only basic spectral editing!
Those intending to upmix mono source material to stereo with professional level results should consider more sophisticated applications which help considerably with achieving higher quality separations as well as help cut down on the time and effort required to produce higher quality results.
SpectraLayers Pro 6, now from Steinberg, includes a harmonic selection tool and has been used on many of the best mono to stereo upmixes created and released commercially to date. SpectraLayers Pro 6 includes a number of tools to help select the desired sounds and has the advantage of being available for both macOS and Windows. SpectraLayers Pro 6 now includes an ARA 2 plug-in which allows it to be used directly from within a compatible DAW.
Audionamix recently updated their XTRAX STEMS application to a subscription-based application. XTRAX STEMS is a cloud-based application, available for both macOS and Windows, which takes a mono or stereo source and separates it into four stems: drums, vocals, bass, and the remaining music. You can easily export the separated stems to refine them in a spectral editor.
Acoustica Premium Edition 7.2, from Acon Digital, is a reasonably priced application which includes spectral editing capabilities with harmonic tracking. The spectral editing capabilities, available only in the Premium Edition, include brush, freehand or magic wand selection tools. Acoustica Premium Edition 7.2 includes their new Remix tool, based on Spleeter, which can separate a mono or stereo source into up to five stems. Acoustica Premium Edition 7.2 is available for both macOS and Windows.
Another inexpensive spectral editor worth considering is the newly updated iZotope RX 7 Elements. iZotope RX 7 Elements includes the important Harmonic Selection Tool as well as the revolutionary intelligent Repair Assistant which can detect noise, clipping, clicks, and more, and then offer different processing options to repair your content. It also offers Voice De-noise, De-clip, De-click, and De-hum tools.
The new iZotope RX 7 Standard and iZotope RX 7 Advanced applications offer very comprehensive suites of tools which are well designed... powerful, yet easy to use. They both offer sophisticated spectral editing capabilities including the important Harmonic Selection tool. Both also include the revolutionary new Music Rebalance module which uses machine learning to allow you adjust the levels of the vocals, bass, percussion, and the remainder, independently!
In addition to harmonic selection capabilities, the spectral editor in WaveLab Pro 9.5 includes a new Wavelet display for a more accurate visual representation of the musical content, as well as Patent-pending Audio Inpainting technology to recreate and/or replace corrupt audio material by logically using the spectral information of the surrounding area.
DeMIX Essentials, from AudioSourceRE, is an easy to use sound source application which allows you to quickly separate vocals, drums, and other instruments from mono or stereo source material. DeMIX Essentials includes a built-in mixer which allows you to hear your separated tracks in the context of a stereo mix. DeMIX Essentials is available for both macOS and Windows.
DeMIX Pro, also from AudioSourceRE, is a powerful application which includes advanced sound source separation capabilities as well as a built-in full-featured spectral editor. DeMIX Pro includes cutting edge automatic drum and vocal separation capabilities as well as a unique Melody Editor which allows for guided vocal and instrumental separations, even in the presence of harmony vocals and other instrumentation. DeMIX Pro includes a built-in mixer which allows you to hear your separated tracks in the context of a stereo mix. DeMIX Pro is available for both macOS and Windows.
ACID Pro 10, from MAGIX, includes an updated version of zynaptiq® STEM MAKER audio source separation technology. According to MAGIX, "Algorithms based on deep learning, as well as patent pending DSP algorithms split your tracks into vocals, drums and music, so you can use these results in your own music and remixes." Denis Goekdag, CEO of Zynaptiq, indicates that "ease of use is maximized with this one: you just tell the thing to DO IT and that’s that, no parameters, no manual selection"!
Deezer Research recently introduced Spleeter, a free open-source Python library based on TensorFlow that makes use of deep learning to perform state-of-the-art source separation on your mono or stereo audio and provides 2, 4, or 5 stems in return. Spleeter is a command line tool with no GUI (graphical user interface). Those wishing to make use of Spleeter, but are wary of installing and using a command line tool, may wish to try Moises which provides a web-based service for Spleeter. Moises is currently available free of charge. Two other web-based services for Spleeter are Ezstems and Splitter.
Let's Unmix is an app for the iPad and iPhone which can separate a mono or stereo source into four stems through the use of Deep Learning: vocals, drums, bass, and the remaining music.
I should point out that results with any of these applications are still highly dependent upon the source material used. Higher quality sources that are not highly compressed and contain fewer sound sources are easier to separate, and help produce higher quality, more pleasing stereo mixes. There are countless mono recordings that can benefit from being upmixed to stereo through the use of this technology. As the applications continue to improve and additional automation is added to the processing, the amount of time and effort needed to produce professional level results will decrease.
Please understand that I can't guarantee the quality of the results with any of these applications. It is important for the user to evaluate the applications themselves to insure that they will meet their needs. I highly recommend trying the product demos prior to purchasing any software.
I will update my recommendations as new applications and additional new features become available. Your questions and comments regarding this technology are always welcome. Please feel free to email me at firstname.lastname@example.org or use the contact form on the CONTACT page of this website.
Updated March 21, 2020