Snap Permissions
If you get an error message while trying to import your music from an external HDD/device, then you likely need to enable this permission.
To do so, locate Tauon Music Box in the Software Center, and click Permissions:
Then, make sure the setting "Read/write files on removable storage devices" is enabled:
This can also be accomplished on the terminal with the following.
sudo snap connect tauon:removable-media :removable-media
Details: This setting extends access to
/media,/run/mediaand/mnt.