Split Tracks and Pulseaudio

Thu, Feb 11, 2021

I’m learning to play the drums. Something I’m trialling is split tracks, where the mix of the recording is separated into left and right, with left being only drums and vocals, and right being everything except drums and vocals. This is great except when played through stereo headphones, the mix sounds odd and is uncomfortable to listen to. The solution is to convert the stereo output to mono, however most home setups won’t have the kind of gear required for this.

My solution is to use Linux Pulseaudio to create a ‘sound sink’ which is essentially a virtual output device that sits between my music player software and the sound card.

I added 3 lines to the end of /etc/pulse/default.pa - each one creates a new sound sink, in addition to the normal stereo output.

load-module module-remap-sink sink_name=Mono sink_properties="device.description='Stereo to Mono'" master=alsa_output.pci-0000_00_1b.0.analog-stereo channels=2 channel_map=mono,mono

load-module module-remap-sink sink_name=Left-to-Mono sink_properties="device.description='Left to Mono'" master=alsa_output.pci-0000_00_1b.0.analog-stereo channels=1 master_channel_map=mono channel_map=left

load-module module-remap-sink sink_name=Right-to-Mono sink_properties="device.description='Right to Mono'" master=alsa_output.pci-0000_00_1b.0.analog-stereo channels=1 master_channel_map=mono channel_map=right

The first line creates the ‘Stereo to Mono’ sink, useful for listening to both left and right channels of the split track together. Then there is ‘Left to Mono’, useful for listening to drums only - instead of them coming out of only the left headphone, they come out of both headphones. Then ‘Right to Mono’.

When playing back a split track song I can switch between the 3 different sinks in the audio config settings as required.