Soundscape

Allows you to set up sound profiles for each of your characters individually, save and load audio presets, and exposes a few audio preferences not accessible through the default interface.

Type /xss to access the configuration panel, or use the 'Soundscape Config' button at Game Menu > System > Sound

I found myself frequently going to the system settings to do things like turn zone music on and off or to switch between the quieter settings I like when I'm grinding or farming and the more immersive settings I like when I'm doing new content. I started using a set of '/console' macros to toggle various settings and eventually that grew into this addon. It comes with a few 'built-in' presets and allows you to create your own, as well. You can save sound settings by-character, by-account, or a combination of both.