In addition to having a love of Gavin DeGraw's "I Don't Want To Be," we know that the Monster is from the South and has a Cadillac. He mentions that he's going to "rewrite" his mixtape, and prove to audiences that he's more than "puff and fluff." According to the Monster, he was at the top of his game, "but the game turned on" him and he took a break from the public eye.
He also says "not everyone" would consider him a professional singer,
So, who could it be? The mention of mixtapes, the game, and not everyone seeing him as a singer suggests the Monster is a rapper who's trying to break free from being pigeonholed into that genre. If he's indeed a southern rapper, his voice sounds a great deal like T-Pain (from Tallahassee, Florida), who we know from his Tiny Desk performance has a beautiful singing voice, period.