How to custom emms playlist format?

Emacs
1

here is my dir structure:

media
      song
          track1
             1.mp3
             2.mp3
             3.mp3
          track2
             1.mp3
             2.mp3
             3.mp3
      music
            track1
               1.mp3
               2.mp3
            track2
               1.mp3
               2.mp3

i want the emms playlist show them like this:

(indent two space)song
(indent four space)track1
(indent six space)1
(indent six space)2
(indent six space)3
(indent four space)track2
(indent six space)1
(indent six space)2
(indent six space)3
(indent two space)music
(indent four space)track1
(indent six space)1
(indent six space)2
(indent four space)track2
(indent six space)1
(indent six space)2

thanks guys