Great saxophone players do more than just hit the right notes on their instrument, they can also tune their own vocal tract to match, researchers say.

Musicians have long known that professional saxophonists can play very high notes that amateurs simply cannot manage.

Now a physicist from the University of New South Wales explains why.

The best saxophone players have figured out how to change the shapes of their vocal tracts so they resonate at a frequency close to that of the note they're aiming for.

"We measured the resonances of saxophonists' vocal tracts directly, while they played," said doctoral student Chen Jer-Ming, whose work appears in the journal Science.

Over the standard saxophone range of roughly two-and-a-half octaves, there was no particular relationship between the vocal tract resonances and notes played, he says.

But for the highest notes, the vocal tracts of professional saxophonists did something special.

"In those higher frequencies up there, the saxophone's own resonances are relatively weak, so that's why it's hard to sound those notes," Mr Chen said.

"By adjusting your vocal tract resonances to match those in the saxophone, they add up. That allows them to play the notes."

New device

Musicians and scientists have been debating for 25 years the importance of the player's vocal tract in hitting notes on single-reed instruments such as the saxophone and clarinet.

Mr Chen solved that debate by building a device that could fit unobtrusively within the mouthpiece of a saxophone and detect the resonances of the musician's vocal tract.

He and his colleagues used the device to compare three amateur players and five professional jazz and classical saxophonists.

When Mr Chen asked the professionals how they learned to play the high notes, they all said it was something they stumbled upon and kept practising.

"They all told me the same thing," Mr Chen said.

"Once they learned how to do it, they had to hear the note in their head first, then the note will just naturally follow.

"I think it's a kind of muscle memory at work. Their throat just moves in the right places at the right time."

Now the secret is out, Mr Chen says it might be possible to teach budding saxophonists how to adjust their playing to hit those high notes.

"I believe its something most people could learn if they were conscious of it and practise hard," he said.

"It won't happen overnight."