Last fall the actor who portrayed Johnny Cash in the film biopic “Walk The Line” said he was giving up movie biz for the music biz, starting a rap career.

Then earlier this month, Phoenix performed an awkwardly sloppy set in a Las Vegas club, a performance that ended with Phoenix falling down while on stage.

But is this for real? Does Phoenix think he has what it takes to be a music star? Or is something else up?

Probably something else.

Citing a source who recently worked with Phoenix, Entertainment Weekly says it’s all part of a mockumentary being filmed by Casey Affleck.

“It’s a put-on,” the source told EW, allegedly quoting Phoenix. “I’m going to pretend to have a meltdown and change careers, and Casey is going to film it.”

But that’s only the half of it. Evidently Phoenix will continue mining this career-change thing for the foreseeable future.

“It’s an art project for him,” EW quotes another source as saying. “He’s going full out. He probably has told his reps that he’s quit acting. Joaquin is very smart. This is very conscious. He has a huge degree of control.”

Joaquin Phoenix in Vegas.  Don’t expect him to give up his day job anytime soon.