Mariah Carey sang live at last night's Christmas tree lighting in New York City, and proceeded to butcher the you-know-what out of her Christmas classic "All I Want for Christmas Is You".

Carey was supposed to have taped the performance Tuesday night, but NBC execs called it off after she left everyone waiting for three hours. The gossip site TMZ says it was because she was busy talking to her divorce attorney, while E! Online claims she didn't want to perform because it was raining. Either way, the decision to cut her from the show was made.

She was later able to work it out with NBC and allowed back on, but because there was no longer any time to pre-tape her performance, was forced to sing live. Mariah missed most of the high notes she's famous for, leaving her backup singers to pick up the slack, and even missed one note so badly she had to clear her throat before she could finish.

Watch what she sounded like on TV last night with the band and the backup singers behind her in the above video, then compare it to THIS video of Carey's unedited, isolated vocals.