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Last Word is Â鶹´«Ã½’s long-running series in which readers give scientific answers to each other’s questions, ranging from the minutiae of everyday life to absurd astronomical hypotheticals. To answer a question or ask a new one, email lastword@newscientist.com

Professor Andrea Halpern and Professor Katie Overy
Bucknell University, Pennsylvania, and University of Edinburgh, UK

We invite you to imagine the tune of Happy Birthday right now! When you imagine this familiar melody, your ears aren’t involved, but some parts of the brain associated with the auditory system do become active – not usually the primary auditory cortex (PAC), which processes sound signals, but the secondary auditory cortex, which is involved in analysing and organising sounds to make sense of them.

In addition to the auditory system, brain areas associated with working memory (dorsolateral prefrontal cortex) and sequencing (supplementary motor area) also become active. And if you start playing around with tunes in your head (try to imagine the first phrase of Happy Birthday backwards), then areas associated with attention and focus also become engaged (parietal lobe). So, generating a tune in your head actually involves a lot of cognitive skills.

These skills can take place in “real time” – most people can keep a steady tempo in their imagined melodies – and can even be developed. For example, composers and improvisers can create new music in their heads without any sound input. Interestingly, individuals who report more vivid imagined melodies show increased activity in the secondary auditory cortex and more connections between auditory and working memory areas. In contrast, individuals who experience auditory hallucinations actually show a reduction of activity in the PAC (compared with controls) when listening to real sounds. So, for them, the neural signals from real and imagined sounds can overlap in the brain, potentially explaining the confusion.

David Kroop
West Friendship, Maryland, US

If you are a musician, you probably have hundreds of songs stored in your head, complete with the recorded key for each, and all the solos and instrument sounds it was recorded with. If you are a music writer, you probably have the melody snippets and chord progressions stored there too.

The way it works is you hear a song you like (note that ones you don’t like you forget immediately), then play it over and over again in your head, refining its details. After that, it is essentially a permanently stored song. So the tune is heard via the ear, stored in the mind and thereafter played back in the mind and perhaps sung, if you are so inclined.

If you are a musician, that playback will translate into the tune being recreated on the instrument(s) of choice. If you have perfect pitch – meaning you can hum middle C perfectly in tune with no other aid – then the memorised tune will also be in the proper key when played back on an instrument. I can hear a few notes from a song and immediately identify the song and play it back on the piano.

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