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Isolate vocals, audio restoration, simple phase inversion

by Jane is K.O. - 19.01.14

CASE [mostly for music producers and fans of sound quality]
• Original production files are lost, but release is possible – but you are left to stereo files, uncompressed at best. Your guitar player found his own contributions on his hard disk, too. Vocalist has recordings still, which you were using?
• You’d like to get a vocal or instrument isolated, but only have a full mix & that same mix again, but without the respective instrument.
• MP3 doesn’t seem to sound quite as the AIF/WAVE copy from the CD you bought. How to check the difference?
etc…

METHOD
It’s simple substraction: MixA – MixB = 0 only, when they are exactly the same.
So create the difference between (compare) 2 sound files using phase inversion.

In a professional DAW of your choice (we prefer Cubase / Nuendo)
1. Align both files perfectly (sample exact at start).
2. Both play at exactly the same volume, panning. No plugins in channel strips or master.
3. Phase invert one of the files. Some DAW can do this via track control (ø), or you have to create a physical phase inverted copy of the original first (go back to 1. then).
4. Finally play or bounce to hear the difference.

If there’s only one audio file, you can use sonixWORX Isolate, to suppress most of a vocal (or else) in a mix. This is very time and space consuming, an audio file of 4:10 uses up to 40 GB (!) for this here.
Use resulting file to isolate the vocal by using above technique.
If you found other software suitable for this, please comment.

MORE USES
• Finally i used phase inversion myself quite oftenly to attempt to recover from fatal hard disk crash. This takes weeks and months. A recent album, recovered from bad mp3 and a few productions files, hidden on 3 computers of 3 guys in 3 countries, is here:
Vedette – i slept moments for you
Vedette website
• I also used it to find out, if my DAW or plugins work correctly. Discover bad engineering. You can check, if a bypassed plugin is really bypassing or still sounds different to NO plugin at all.
• In recording a common way to use this is, when a singer doesn’t want to use headphones. You record one version with speakers in the room, afterwards you ask the singer just to remain at the mic quietly, while you record one more time. Phase inverse that one along with the vocal recordings to cancel out the majority of speaker noise in in the background.

*Enjoy, and please share, if you like this article.



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