Nine Inch Nails' current lineup remains a work in progress. After bassist Eric Avery's departure and the addition of Robin Finck, Adrian Belew (of King Crimson) has announced his exit from NIN's 2013 incarnation.

He wrote on Facebook, via Consequence of Sound:

hey folks, before this goes too far let me say this: I greatly respect trent and the music he makes. no one is at fault. we both agreed it just was not working. I’m sorry to disappoint anyone. that really hurts. but NIN will do an amazing show and I am back where I belong: creating FLUX.

(FLUX is Belew's solo project.)

That post has since disappeared from Belew's page, replaced by a shorter note: "concerning me being part of the 2013 Nine Inch Nails band: it didn't work."

Prior to that announcement, Belew had been posting regular updates about the status of rehearsals with Nine Inch Nails, sounding very excited-- but also pointing out possible roadblocks.

For example, he wrote in late April: "today started with an excellent conference call with trent and the entire band. it was all about our work method and how we will manage the monumental work load. it will be a TON of head scratching, but worth every minute!"

Belew's exit announcement comes right after Nine Inch Nails unveiled their grand plans for a massive North American tour this fall, as well as the release of the new NIN album Hesitation Marks.

Recall that Belew was instrumental in this year's reformation of Nine Inch Nails, as explained in a statement from Reznor in February. "I was working with Adrian Belew on some musical ideas... which led to the decision to re-think the idea of what Nine Inch Nails could be," he said. Belew does contribute to the album.

Above, listen to the new Nine Inch Nails single "Came Back Haunted".