I’ve been working on this for a long long time…
Currently, the Voice Removal in Audacity lacks the ability to return a stereo sound, nor is it able to isolate the center.
External plug-ins can do that (somewhat) but I thought it would be nice to have such an effect written in Nyquist - where it can be tweaked easily.
Here it is:
rjh-stereo-tool.ny (14.8 KB)
Update from July 16th, 2015
The effect (without rotation, panning etc.) is from now on shipped with Audacity (starting with version 2.1.1)
It is called “Vocal Reduction and Isolation”
It has its own help page online or locally installed.
The following is therefore more or less obsolete:
(Update, you can find a slim version for Audacity 2.1.0 and higher in the following post:
v1.0 July, 1st 2013 v 1.1 faster by about 33 % (3:00 m in 52 s) v1.2: No messaging for aborted or finished preview v1.3: Faster by about 25 % (3:00 m in 37 s; w.o. filter in 1:14 m Added playback for left and right channel Error message for play attempts on non-Windows OS Only one Effect Parameter (context dependant) Remove/isolation split into filtered and not filtered versions Some catalog entries renamed
(A newer feature description will be posted soon)
A short feature description:
- Remove Center - Returns a Stereo version of the center-less track.
- Isolate Center - The center without most of the extreme panned audio (the slope is linearly, so some background will still be audible)
- Same as before, but it can be used on a duplicated track to control the attenuation with the gain control. Both tracks together = no center; New track alone: emphasis of the center (see example below)
- Carousel and Rotary effects - Rotate the Stereo image by degrees/s (Rotary = 90 times faster). Set the degrees under “Stereo Field Rotation”
- Some Fade effects which go in the direction of the set “Pan Angle”. Note that in principle all made settings (rotation, pan, delay and width) influence the outcome of a chosen action from the catalog.
- Fixed Rotation/Panning (…Delay and Width) This applies the current transformation settings without variable modification (or center removal). Useful to apply a single 45 degree Rotation or a widening effect (again, all settings are used simultaneously).
This example illustrates the use of the (inverted) center isolation.
The Options control just does what it says.
Please note that the center removal is very time consuming (but now 50 times faster then my earliest tries). Therefore, I’ve included the ability to play the result while it is calculated.
The nice thing is that the execution can be aborted any time - no bad surprises.
This feature runs badly or not at all on Linux systems!
The analyse option tells you something about the (cross-) correlation of the two channels.
There are 4 controls for Rotation, Panning (gain difference), Delay (panning with time difference) and Stereo Width. The latter has not much impact on the different effects - it is here for completeness sake.
I know that some people will complain that there are too many controls. Although not obvious, they can improve the result for a center removal task. For example, many old tunes are such panned that the voice is on one side and the band on the other. You can try rotating the stereo field by +/- 45 degrees to solve this problem.
You’ll see what I mean if you first apply the Carousel effect and then Removal/Isolation.
There are another three controls:
- Low- and highpass/-cut. Only the frequencies between those values are regarded while removing/isolating.
- Playback control (if you here clipping during a preview).
A last sample sound for now. The (mono) track has been “improved” bwith a over-dimensioned stereo-reverb.
Ive used the Center Isolation to dry it up again.
Have fun - as much as I’ve had so far.