I'm not sure if he has, but why would he ever do that? Unless it was not only production but also engineering/innovating in some sense.
Yep, well that would be interesting in the sense of how you could disrupt the music business by "manufacturing" beats. We've seen some similar progress around machine generated art (e.g. deep dreaming and the like).
I'd sooner expect strong AI than an AI that can actually produce good music purely autonomously.
Who knows what you mean by purely autonomously since even people can't help but learn from their experiences.
Nevertheless, here's a novel composition made by an NLP algorithm trained on classical music: