ROCK legend Freddie Mercury had an unusual "growling" singing technique that gave him one of the most distinctive voices in music, research has shown.
But claims that the Queen singer had an extraordinary range spanning four octaves could not be substantiated by scientists.
The study found that Mercury, who died in 1991, was a natural baritone and had a voice range that was "normal for a healthy adult".
Where he stood out from the crowd was in the way he applied vibrato and distortion to his voice.
As part of their investigation, the researchers had a rock singer imitate Mercury's distorted "growl" style while filming his voice box in action with a high-speed camera running at more than 4,000 frames per second.
Using a technique normally employed to test for cancer of the larynx, the camera was attached to a flexible tube passed through the nose and into the upper air passages.
It showed that belting out Freddie-style generated unusual undertone frequencies, or subharmonics - a trick also employed in a more extreme way by traditional Tuvan throat singers from Mongolia.
The scientists led by voice expert Dr Christian Herbst, from the University of Vienna, wrote in the journal Logopedics Phoniatrics Vocology: "Their occurrence aids in creating the impression of a sound production system driven to its limits, even while used with great finesse.
"These traits, in combination with the fast and irregular vibrato, might have helped create Freddie Mercury's eccentric and flamboyant stage persona."
Tuvan throat singers are able to produce two, three or sometimes even four pitches at the same time. The sound has been compared to that of a bagpipe.
Mercury's voice was once described as "a force of nature with the velocity of a hurricane".
In songs such as the smash hit single Bohemian Rhapsody he demonstrated his ability to switch from a powerhouse delivery to the most delicate and fragile vocal expression.
The scientists, who analysed archive recordings and interviews, concluded that Mercury was probably a baritone who sang as a tenor with exceptional control over his technique.
He rejected an offer to sing as baritone in an opera duet with the singer Montserrat Caballe because he feared his fans might not recognise his voice.
