I probably don't understand fully the concept of taxonomies in general, but it seems strange to me that the a custom taxonomy would inherit from Tag? What is the relationship between a taxonomy and a tag? In prose I mean, not in code. What is the result of applying the tag taxonomy as well as a custom one in terms of end-user experience on a hypothetical front-end of what this CMS would power, that is, what would the simplest example of the playlists taxonomy allow one to display?