An American stage hypnotist has fallen to his death at a Sydney apartment block.

Scott Lewis was in Australia to perform with the Illusionists 2.0 magic troupe at the Opera House when his body was found on a fourth floor balcony at Pyrmont.

Witnesses told police they saw an object fall at least six storeys down at the Goldsbrough Mort apartments.

Tourist Rachel Waack, who was staying at the flats, told the website that she was woken by a 'whoomp' noise soon after 9pm.

Waack said: "I went out to the walkway outside our apartment and saw a woman walking along with her head in her hands, screaming.

"She was saying 'Do they know? Do they know?' Then we saw the police arrive soon after that."

He was pronounced dead when ambulance crews and police arrived.

Officers say there are no suspicious circumstances, but there will be an inquiry to investigate whether Dr Lewis was climbing from one balcony to another when he fell.

Dr Lewis, 50, was reported missing by fellow members of Illusionists 2.0 when he failed to arrive at an 11am matinee performance at the Sydney Opera House.

Dr Lewis was the host of the longest running hypnosis show in Las Vegas history where members of the audience are hypnotised on stage to perform outrageous acts.

He headlined his own hypnosis show at the Riviera Hotel for more than nine years.

Dr Lewis, a clinical hypnotherapist, also authored a number of self-help books involving hypnosis to help quit smoking and lose weight and a motivational speaker.

In a joint official statement from the Sydney Opera House and The Illusionists 2.0 Company it read: "We wish to express our deepest sympathies to Dr Lewis' family and friends, as well as to the cast and crew of The Illusionists 2:0. Dr Lewis was a wonderful performer and he will be greatly missed.

"The company is deeply saddened by the sudden loss of Dr Lewis," said Tim Lawson, co-producer of the show. "The entire company has decided to continue the show in his honour, and send our heartfelt condolences to his family and friends."

Thirteen shows involving Dr Lewis and a cast of magicians and illusionists were scheduled at the Opera House from 9-16 January.