Magiera said the whole performance was staged
Tenor Luciano Pavarotti was miming during his last performance at the winter Olympics in Turin in 2006.
Conductor Leone Magiera has revealed the singer's rendition of Nessun Dorma was pre-recorded, as a live performance would have been "too dangerous".
Pavarotti, who died in September, was already suffering pain months before being diagnosed with pancreatic cancer.
Magiera said: "The orchestra pretended to play, I pretended to conduct and Luciano pretended to sing."
He added: "It came off beautifully, no one was aware of the technical tricks."
The revelation came in Magiera's new book Pavarotti Visto Da Vicino (Pavarotti Seen From Close Up), which was published last month.
He said Pavarotti - with whom he worked for many years - recorded the famous aria from Puccini's Turandot in a studio in his home town of Modena, and the orchestra pre-recorded its part separately.
"His voice was nearly intact," Magiera recalled in the book. "He found the strength to repeat it until he was completely satisfied. Then, he fell back on his wheelchair and closed his eyes, exhausted."
Terri Robson, Pavarotti's former manager, said the decision to lip-synch was made because of the cold during the outdoor evening event.
Robson said the tenor's voice was "in great shape... but because of the extreme late-night temperature in Turin in February, for both him and the orchestra, it was decided that the only way to make it work was for him to pre-record."
Pavarotti was diagnosed with pancreatic cancer in the summer of 2006 as he was preparing to leave New York to resume a farewell tour.
He underwent surgery in early July, and his remaining 2006 concerts were cancelled.
Earlier that year he had postponed five dates in June because of what was described as complications from back surgery.