Board Thread:News and Announcements/@comment-4556650-20140411113722/@comment-3544775-20140812173840

There is no preview for the OP and ED songs. It was only announced who will perform them. As for on what songs have these groups worked you can check site like AniDB


 * Ikimonogakari - http://anidb.net/cr6756
 * Flow - http://anidb.net/cr4228
 * Granrodeo - http://anidb.net/cr9293

As for some their old songs: note: none of those songs will be featured in Nanatsu, these songs are just samples of their previous works.
 * Ikimonogakari - Blue Bird - https://www.youtube.com/watch?v=bpJcU9MBd0Y
 * Granrodeo - Can Do - https://www.youtube.com/watch?v=3GwAkthbKMc
 * Flow - GO - https://www.youtube.com/watch?v=V6TTavJAGAQ