Premise: Solo Day is the fifth mini-album released by B1A4 under WM Entertainment. The album was released on July 14, 2014 by WM Entertainment and their distributing label Pony Canyon Korea. The title song of the album, "Solo Day, was produced by leader Jinyoung along with 5 other tracks in the album. CNU also produced 1 song in the album.
Hypothesis: B1A4 sang vocals on all the tracks on their album Solo Day.