We're making changes to the entire tag system.
Genres have been replaced with "Mashup", Original" and "Remix" tags in the sidebar.
At the moment they return tracks tagged as such by the uploader, which gives us a situation where the "original" tag is full of mashups.
We will be adding a checkbox on the upload page to select ONE of the options (mashup, remix, original, and likely DJ-mix and podcast/radio too), then the tags will work as intended.
