You've probably been tormented by a catchy song playing over and over in your head. Spare a thought then for those people for whom this phenomenon is taken to the next level: the song or songs sound real and they play round the clock. They have what's called 'musical hallucinosis'.
Besides hearing music that isn't there, such people often have no other psychological complaints. Now Ramon Mocellin and colleagues have described three typical cases and proposed a tentative neurobiological account of why the condition occurs.
Case one was an 82-year-old patient who lived in a remote farm house. She reported loud music to the police and even sent her husband driving round the neighbourhood looking for the source. She eventually realised the music was a 'trick of her imagination'. Apart from deafness, the woman had no other neurological or psychiatric abnormalities.
Case two was a 62-year-old surfer. He heard the opening bars of Jimi Hendrix's Voodoo Child for six months, when there was really no sound there. This man had mild deafness and smoked cannabis but otherwise had no other relevant medical history.
The last case, a 78-year-old, was profoundly deaf, had Alzheimer's disease and lived in a care home. He heard hymns and songs that were popular in the 1940s and 50s. Although he had cognitive impairments associated with dementia, he had no other psychotic symptoms besides hearing music that wasn't there.
Ramon Mocellin and his colleagues explained that people with musical hallucinosis generally realise that their auditory experiences are a trick of the mind, thus distinguishing their symptoms from the hallucinations experienced by people with psychosis, who generally believe their unusual perceptions are real.
As demonstrated by the above cases, musical hallucinosis is often associated with deafness and Mocellin's team think the condition may reflect the spontaneous, aberrant firing of those brain cells whose job is to process music, if there were any to be heard. Higher brain levels then seek to make sense of this spontaneous firing, often drawing on musical memories in the process - hence the common experience of perceiving music from previous eras.
Link to article on musical hallucinosis published in The Sunday Telegraph in 2004.
Mocellin, R., Walterfang, M., Velakoulis, D. (2008). Musical hallucinosis: case reports and possible neurobiological models. Acta Neuropsychiatrica, 20(2), 91-95. DOI: 10.1111/j.1601-5215.2007.00255.x