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.
DeMIX Pro, from AudioSourceRE, is a powerful application which includes advanced music source separation capabilities. DeMIX Pro includes cutting edge vocal separation capabilities, including the ability to automatically separate lead vocals from backing vocals and harmony vocals! DeMIX Pro includes a built-in mixer which allows you to hear your separated tracks in the context of a stereo mix. The latest version of DeMIX Pro, Version 4.2, now includes the ability to perform your separations locally on your computer, as opposed to in the cloud, and also now includes improved bass and drum separations, as well as the ability to separate piano and string instruments. DeMIX Pro is available for both macOS and Windows. Highly recommended!
SpectraLayers Pro 9, from Steinberg, includes a harmonic selection tool. SpectraLayers Pro has been used on many of the best mono to stereo upmixes created and released commercially to date. SpectraLayers Pro 9 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 9 includes a AI-powered Unmix Stems tool to automatically unmix your audio into as many as five stems. A pattern finder will automatically search your audio file for similar sounds. SpectraLayers Pro 9 includes ARA 2 support which allows it to be used directly from within a compatible DAW. Highly recommended!
Acoustica Premium Edition 7.4, 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 7.4 includes their Remix tool, based on deep learning, which can separate a mono or stereo source into up to five stems. Acoustica Premium Edition 7.4 is available for both macOS (including Native Support for Apple Silicon) and Windows.
The new iZotope RX 10 Standard and iZotope RX 10 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 and improved Music Rebalance module which uses machine learning to allow you adjust the levels of the vocals, bass, percussion, and the remainder, independently! Highly recommended!
Deezer Research 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.
Hit'n'Mix has introduced two new applications: RipX DeepRemix and RipX Deep Audio (which includes RipX DeepRemix). RipX Deep Audio uses the power of AI to separate your mono or stereo audio source into stems, making it useful for upmixing mono source material to stereo.
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 email@example.com or use the contact form on the CONTACT page of this website.
Updated May 20, 2022