Mariah Carey -- PAINFUL Lip Syncing Fail (VIDEO)

Mariah Carey would have been better off pretending to faint during her concert Friday night, because pretending to sing was just an epic fail.

Mariah was performing at the 2015 Jazz and Blues Festival Friday, when everything just went to hell.

It starts off bad and then ... well as Reese says, it's just beyond. She mixes lines, forgets the words and almost just gives up.

It's almost like a blood sport. Are people going to her concerts to hear her sing, or watch what you see in the video?