To have a live removal of vocals from a stereo recording we can add a LADSPA filter as a sound output to pulseaudio. There is a quite good karaoke plugin from the Steve Harris' LADSPA Plugins which will remove central vocals from a stereo recording, and which can also be used with Audacity.
These plugins will be installed with the package swh-plugins . The amount of voice removal and consecutive mono conversion is given as control parameter in dB.
To apply the effect we need to know the pulseaudio name of our default audio sink with
The default sink name is marked with an asterix like in the example below:
* index: 1
We can then apply the karako filter with the following command
pactl load-module module-ladspa-sink sink_name=Karaoke master=<name> plugin=karaoke_1409 label=karaoke control=-30
<name> with the name of your audio device (e.g.
Note down the module number given as output from above command in case we want to remove it again (
pactl unload-module <nmber>). All modules are removed and default are reset with
control parameter gives a voice removal of
-30 dB here, higher values (i.e. less negative like
-10) for more vocals (but better music), lower values (i.e. more negative like
-60) for even less vocals but also more original music removal. Positive values are possible but they will lead to heavy distortions.
Choose this newly created audio output sink as output in your sound setting before you start playback of your music player.
Note that not all music recordings are suitable for this karaoke plugin, the more central the vocal stay the better. Mono recordings will not work.