Forget waterboarding, Guantanamo Bay prisoners are now being tortured by BIG BIRD -- at least according to a new documentary released by Al Jazeera.
According to the doc -- called "Songs of War" -- detainees at the U.S. Naval base have been forced to wear headphones blaring Sesame Street music on repeat for hours or days on end ... to break their will (start at 2:00).
Award-winning Sesame Street composer Christopher Cerf tells Al Jazeera, "My first reaction was this just can't possibly be true ... "
Cerf says, "Of course I didn't really like the idea that I was helping break down prisoners, but it was much worse when I heard later that they were actually using the music in Guantanamo to do deep, long-term interrogations and obviously to inflict enough pain on prisoners so they would talk."
Reports surfaced in 2008 ... heavy metal like Metallica was used to torture people at Guantanamo -- but we gotta say, Sesame Street might just be worse.