Holy cow, this is beautiful. Best Michael song I've heard in a decade.
Unsurprisingly, it's an oldie that never got a release. Billbiard says:
According to the song's description on Ping, "Much Too Soon" was "written at the time of 'Thriller,'" and Jackson "always liked the song but never found the right home for it." The ballad was written by the singer and co-produced with John McClain, the co-executor of his estate.