The goal of turning musical omelettes back into eggs gets ever closer, thanks to some unlikely cloud-based DSP wizardry!
Audio engineering goes hand in hand with the tendency to be a control freak. We chafe if we can't move the musicians around on the studio floor, or tweak the settings on their amplifiers, or substitute our own mics for their favourite stage model. We close-mic so that we can choose artificial ambience later, and DI so that we aren't wedded to a particular guitar sound. We obsess about separation in order to give ourselves the maximum freedom to manipulate individual sources.
In short, there is nothing so upsetting to the modern audio engineer as the thought that something is what it is and can't be changed. Until now, though, we've always had to accept that some recordings just are like that. Records made direct to a mono or stereo master, flawed mixes made from multitracks that have since been wiped or destroyed, live recordings captured on handheld devices: all are now what they are, fixed and immune to our obsessive need to tweak.
Or are they?
Over the last few years, clever people at the bleeding edge of DSP development have been beavering away to undermine the idea that any recording has to be considered a finished artifact. The resulting technology has earned the name 'source separation', and allows a single recording to be broken down into separate tracks representing individual vocal or instrumental sources. These can then be reprocessed, rebalanced and remixed until we run out of time or our desire for control has finally been satisfied.
Up to now, the market leaders in this field until have been Audionamix, who offer a range of tools targeting serious professionals in the worlds of music production, audio restoration, film, TV and broadcast, as well as the more affordable and largely preset-based XTRAX Stems. However, last November's AES Show in New York introduced a rival technology. AudioSourceRE (pronounced 'audio sorcery') are a company set up to commercialise the work of Irish academic Dr Derry Fitzgerald, who has spent nearly two decades studying the problem of source separation. Fitzgerald's expertise has already been put to work on projects that include Beach Boys remixes, but this is the first time that his algorithms have been made available to the general public.
Available in a full-fat Pro and a more affordable Essentials version, DeMIX is a stand-alone program that runs on Mac OS and Windows, and is authorised to an iLok account. As with Audionamix's tools, the heavy DSP lifting for source separation is performed remotely on a cloud server, so a fast Internet connection is essential. However, DeMIX does have another string to its bow in the shape of spectral editing, which is carried out locally and works fairly conventionally (see box).
Philosophically speaking, DeMIX has another key feature in common with Audionamix's approach, namely that the basic act of separating a track into two or more source elements never undermines its overall integrity. Provided you don't alter the level or pan position of those separated elements, or process them in some way, they will perfectly recombine to reproduce the original recording.
Beginning a separation in DeMIX is as easy as dragging in an audio file in WAV, AIFF, MP3 or FLAC format. You can then hit one of the three buttons at the top of the window that trigger different types of source separation. The most basic of these, as far as the user is concerned, is Drums, which offers only one option, labelled 'stereo smoothing'.
More novel, and more complex, is Pan, which separates sources depending on their positions within the stereo field — one of those ideas that is easy to grasp conceptually, but rather harder to implement in DSP! You can use this to split out as many as seven separate sources, the...
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