In most cases, the music is familiar to the patient

Dr Eva Schielke

A case study reported in the journal Neurology involved a 57-year-old German who developed continuous hallucinations consisting of men's and children's choruses singing folk songs.

The hallucinations came on while he was in hospital, having complained of symptoms including dizziness and numbness, which, after a brain scan, turned out to be an abscess containing bacterial meningitis.

Antibiotics were used to tackle it, but during his recovery the strange music started.

Dr Eva Schielke, a neurologist at the University Hospital in Berlin, said: "He only became aware of the hallucinations several hours after they began - he had expected to find a carnival or celebration in the schoolyard next to the hospital."

Despite the antibiotics treating the abscess, the imaginary sounds lasted for five weeks - he left hospital 11 weeks later.

However, doctors believe that it was the location of the abscess that was key to the hallucination.

The region of the brain, called the dorsal pons, has been associated with other cases, although only a handful have ever been reported.

All suffered from severe disorder stroke, brain haemorrhage or encephalitis, and had abnormalities of that part of the brain.

Range of tastes

However, the type of music endured by the patient varied widely from country to country.

Dr Schielke said: "A French patient heard popular French chansons, another heard Mozart and a Canadian patient heard Glenn Miller big band music.

"In most cases, the music is familiar to the patient. Our patient, for example, heard folk songs which he liked to listen to before."

Researchers have the theory that these hallucinations are triggered by disruption in the communication pathways between different parts of the brain.

It may limit the function of nerve cells that stop the brain from hallucinating.

Older people suffering from chronic and extensive hearing loss do complain of similar musical hallucinations, although these are thought to be brought on by sensory deprivation.