After I went deaf in my right ear (see this and this), it became somewhat annoying to listen to songs that employ heavy panning, such as the guitar part in Herbie Hancock’s Watermelon Man (Head Hunters). To fix this, I made a quick bash script that, through PortAudio (the audio API used by KDE until recently), creates a new virtual playback device (or virtual sink) that mixes the left and right channels to mono.

However, after installing Arch Linux on my new laptop, I discovered that the new default for audio device controls is PipeWire, which has similar features and capability, but broke my script’s functionality.

I had to switch from using the pacmd command to pactl, as only the latter was compatible with the new PipeWire based installation. After some tweaking and adapting the script to the new command, the script looks something like this:

#!/bin/bash
if ! pactl list sinks | grep mono_aud > /dev/null; then
        pactl load-module module-remap-sink master=alsa_output.pci-0000_06_00.6.analog-stereo sink_name=mono_aud sink_properties="device.description='Mono'" channels=1 channel_map=mono
        echo "Global Mono Audio enabled."
else
        echo "mono audio already enabled."
fi


Essentially, it’s almost just an alias for the below command, which creates a virtuial sink (essentially a virtual device) that when selected, takes the audio output of my laptop, down mixes it to mono (hence the channels=1 channel_map=mono), and then feeds it to its master device, in this case alsa_output.pci-0000_06_00.6.analog-stereo, which is the id of my laptop’s audio card.

pactl load-module module-remap-sink master=alsa_output.pci-0000_06_00.6.analog-stereo sink_name=mono_aud sink_properties="device.description='Mono'" channels=1 channel_map=mono

If you’re curious as to where to find the id of your audio card, you can run pactl list sinks, which should give you the names of all real and virtual audio devices on your system; it is from here that I obtained the name alsa_output.pci-0000_06_00.6.analog-stereo.

The difference is that the script first uses an if statement to check whether a virtual sink with the name `mono_aud’ already exists, and only makes the new sink if none exist.

I named the script monoAUD for mono audio, and I put it in my bash scripts directory, which is added to $PATH by my .bashrc file. This way, whenever I want mono audio, I just have to type in monoAUD into a terminal, and boom, the new virtual device is created and automatically selected by my desktop environment. Problem solved; now I can hear all parts of all songs, regardless of how they’re mixed :D