Mechanism behind trumpet playing robot?

a cavity of the chest, the scraggy neck seemed to be
bending double under the weight of the skull. At a guess he would have said
that it was the body of a man of sixty, suffering from some malignant
disease.
'You have thought sometimes,' said O'Brien, 'that my face -- the face
of a member of the Inner Party -- looks old and worn. What do you think of
your own face?'
He seized Winston's shoulder and spun him round so that he was facing
him.
'Look at the condition you are in!' he said. 'Look at this filthy
grime all over your body. Look at the dirt between your toes. Look at that
disgusting running sore on your leg. Do you know that you stink like a
goat? Probably you have ceased to notice it. Look at your emaciation. Do
you see? I can make my thumb and forefinger meet round your bicep. I could
snap your neck like a carrot. Do you know that you have lost twenty-five
kilograms since you have been in our hands? Even your hair is coming out in
handfuls. Look!' He plucked at Winston's head and brought away a tuft of
hair. 'Open your mouth. Nine, ten, eleven teeth left. How many had you when
you came to us? And the few you have left are dropping out of your head.
Look here!'
He seized one of Winston's remaining front teeth between his powerful
thumb and forefinger. A twinge of pain shot through Winston's jaw. O'Brien
had wrenched the loose tooth out by the roots. He tossed it across the
cell.
'You are rotting away,'