Hierarchical tags

Hello Andrei
Have you thought about the hierarchical tags?
Here's what I have in mind -
Let's say I tag a file with -> music, english, dance, oldies, 70s

Now if there is a feature provided in the Manage tags that allows me to assign the parent, child tags then it would be great. Then you can provide a windows explorer like UI where you have folders and sub folder on left side and file list on the right side.
So if I arrange my tags as
music
  english
     dance
     oldies
         70s

In the explorer window I can see english as one of the top level folders and below that will be dance and oldies. Under the oldies, will be another sub folder of 70s.
When I click on english, it will show me all the songs that are tagged with english. When I click on dance, then it will show me all the songs that are tagged as english AND dance (you already provide this kind of functionality with tag cloud but this is explorer view).