A small Python script created for the sole purpose of controlling the volume on your local Linux Spotify desktop client from the commandline. If you are using a desktop environment you can just add a global shortcut to the script for ease-of-use.
<path/to/script>/spotify_sink_identify_volume_changer [up/down]
Pre-reqs: PulseAudio, pactl and Python3
The script is provided as-is and all credit for the original script goes to Marcin Kocur.