Bwa-ha-ha...
Enrique muy bueno
This was originally "outed" on a Howard Stern broadcast back in 2000 (I actually happened to hear that one) and described as what he actually sang in the studio prior to post-recording processing.
However, it's also been said that this was a recording sneaked by a stage technician while he was lip-syncing a performance.
I'll believe the latter. He still sucks.