Aparently they come with this CD. http://www.amazon.com/Last-Note-Setsuna-Japan-QWCE-288/dp/B00CPYDQPU
http://www.vocaloidotaku.net/index.php?/topic/42036-exit-tunes-presents-setsuna-code-last-note-feat-gumi%E3%80%81%E5%88%9D%E9%9F%B3%E3%83%9F%E3%82%AF/