Audacity is a free and open-source digital audio editor and recording application software, available for Windows, macOS/OS X, and Unix-like operating systems.
Audacity can be used for post-processing of all types of audio, including podcasts by adding effects such as normalization, trimming, and fading in and out.
Case 1: Vocal Removal with vocals in the middle and instruments spread around them
Vocal Removal is a technique in which the vocals are panned in the center of a stereo track. This process can sometimes be effective by removing what is same to both tracks (i.e. the vocals), leaving behind what is different (i.e. the instrumentals).
Vocal Removal in the Audacity is used to seperate the stereo track into different channels, make both mono, invert all of one of them then play back the result.
It should be noted that, everything which is panned in the center is removed, not just vocals, and returns a dual mono result.
In some music this could mean removing instrumental parts. Removal of the vocals can often be incomplete leaving artifacts behind; this is especially true where there are backing vocals or where reverb has been applied as this spreads sound sources and makes them very hard to extract from each other.
There is a special effect found in Audacity named as Nyquist plug-in effect which is used to automate the steps involved in Case 1, at “Effect > Vocal Reduction”. If you only wanted to automate Case 1 in the Vocal Reduction effect, you only have to choose the option “Remove Center Classic (Mono)”. As it is going to remove the whole frequency spectrum of center-panned audio and returns a dual mono track.
Case 2: Vocal Removal with vocals in one channel and everything else in the other
If you have such a stereo track where the vocals are mixed with each other into one channel and everything else hard into the other channel you can easily split the stereo track into separate channels then delete the vocal channel.
It is quite easy to “split a stereo track”, you just have to click on the downward pointing arrow at the top of the Track Control Panel then click on Split Stereo to Mono.
If you want to delete a channel, click the [X] to the left of the downward pointing arrow. If you accidentally delete the wrong channel, use Edit > Undo to have it back.