On a January evening at a restaurant in Mexico, El Jefe patiently waited for his name to be called by the karaoke host. When it was, he gently walked to the stage in a pink baseball hat and black, thick-rimmed glasses. As he approached, the host gave him instructions on how to use the microphone. "You've got to hold it up here and just don't yell in the mic," he said, illustrating as El Jefe…