Linus Norda is the one who did a good chunk of the numbers, Shall We Skate, Serenade for Two, Welcome to the Madness, etc. He’s the singer of Theme of King JJ on the actual track!
Jovette Rivera
is the one who did Intoxicated (and sold it as Chris, wowowow).
A Tale of a Sleeping Prince was done by Aisha.
Matt Cab and WISE are the two gentlemen who did Still Alive.
And the Stammi Vicino duet was sung by
Kudō Kazuma and
Matsubara Rinko.