六歌 (Rocka), ( 六歌 (Rocka)) - is vocaloid producer who debuted nico nico douga at 2010. Rocka is a part of circle 灰色Logic. Discography: Dramatic Irony Rocka feat. vocaloids 2011 Venom Ex Machina Rocka feat. vocaloids 2011 俯瞰的ショウタイム Rocka feat. vocaloids 2012 http://twitter.com/rocka_cmh http://www5.atwiki.jp/hmiku/pages/13695.html