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Are there are any VSTs that automatically remove the main harmonic content from an audio source?

For example: if I have a simple sine wave this VST would return absolutely nothing, silence.

If the sine wave has been previously distorted a bit, then this device would return at least some of the noise produced by the distortion, omitting the frequency of the original sine wave.

What I am looking for is a tool that does not only automatically remove one single frequency, but a set of frequencies that might be harmonically related. For example, passing a pure sawtooth trough the device would also return silence.

I think that a device like this has to exist already. Any ideas?

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Izotope RX has a tool called de-construct, which is basically a mixer between the tonal and noisy parts of a sound, tonal being the partials that are related.

To achieve what you want you set the tonal gain fader to -inf (the lowest).

It is not a real time tool, though.

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I believe such a tool would first have to know how to determine what the un-noisy signal sounded like. I don't know of a tool that will do all of this together, but you might be able to cobble together a rudimentary version of such a tool from existing tools. I don't know how well it would work...

For example, Reaper (and probably most DAWs) has a noise-removal filter plugin that first builds up a noise signature spectrum from a snippet of silence, then creates a filtered version of your track without that noise. In theory, you could try saving the output to a new track, inverting it, and mixing it back with the original signal. I have a feeling this wouldn't provide anything particularly useful, though.

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    Thanks for the answer. But I need to make sure that the phase is preserved. If there is any kind of micro-delay or complex operations from FFT data, the phase information may not be preserved. – fstab Oct 23 '14 at 2:07
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Uh, a triangle wave may very well be a distorted form of a sine wave, so you may want the result for a triangle wave to be simultaneously nothing and something according to your task description, depending on the unavailable history of the triangle wave.

It may well be that this may mean that your problem is not merely ill-posed but may not in general have a viable solution. So perhaps you need to narrow down more what you want to achieve.

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this is possible if up to the point you can detect root notes, and subtract a delayed version of the signal from itself whose delay time corresponds to the period of the root note. it probably wont work as well as youd hope it would, and with each increasing note needing filtered out it becomes a tougher cookie to track. and if you dont keep track of how many notes need to be deleted and keep subtracting 7 increasingly delayed periods of sound the resonance will start to sound very angry with you. anyway, i've pretty much built something exactly like this for realtime. i'll shortlist you for a lifetime personal use license but this one is staying proprietary

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