Add articles to a collection from the article or collection?

I'm building a song and a playlist manager. Where should I put my join interface, in the song view or in the playlist view?

Is it better to:

  1. enter the detail view of a song
  2. select "add this song to a playlist"
  3. select a playlist to add it to

Or:

  1. enter the detailed view of a playlist
  2. select "add a song to this playlist"
  3. select a song to add.