[LAU] Filtering out everything but the centre position in stereo

[Jeanette C.]

Hey hey,
is there an effect or a method to filter out everything from a stereo file but 
the "centre"? A sort of reverse karaoke effect.

In theory I'd know what to do, just not how to achieve it. i.e. find all the 
differences between the channels and subtract the respective difference from 
each channel.

Any good tool/plugin or method to implement in something like Csound is 
appreciated.

Best wishes and thanks,

jeanette

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