As mentioned, Nick Cave discussed some of his favorite band/artist tees in response to a question about artist merch on his Red Hand Files website, and while talking about his Flatbush Zombies tee shirt, he also spilled the beans on the existence of an unreleased collaboration he made with the Brooklyn rap trio:

I also own a very beautiful Flatbush Zombies T-shirt, bought around the release of their first album. A few years ago the Zombies and I attempted a collaboration and I sent them my version of the T. Rex classic, “Cosmic Dancer.” They said they “could not relate to it” but they radically pitch-shifted my voice, sampled it and used it anyway, as the percussive heartbeat to an extraordinarily wild and fucked-up piece of hip-hop that neither of us released.

UPDATE: Flatbush Zombies tweeted this:

Hopefully soon!

If anyone reading this has the power to release that song, please do so!!