39 years after its initial release, Wham!’s ‘Last Christmas’ has finally topped the Christmas charts. With that in mind, it poses the question, what makes a song a hit? What magic formula does ‘Last Christmas’ contain that keeps our brains coming back to it year after year?

While pottering about doing jobs, or going for a drive, we often catch ourselves absent-mindedly singing under our breath. Or when trying to go to sleep, there’s usually a song circulating in our head that we can’t get rid of. There appears to be a subconscious part of our brain that hangs on to songs in an incredible way.

When recalling a song we enjoy, our brains must not only be able to remember and access the lyrics, but the varying pitches, tones, rhythms, and, if you’re a particularly keen singer-alonger, the instrumentation as well. Musicologists and psychologists have conducted extensive research into what makes songs “catchy”. What is it about some songs that make them stick in your memory after just one listen and spontaneously sing in your head when you’re trying to focus in a lecture?

“There appears to be a subconscious part of our brain that hangs on to songs in an incredible way”

The most obvious element of a catchy song is melodic simplicity and snappy hooks that come back around: repetition, repetition, repetition. The more you are exposed to the same hook or chorus, the more embedded it becomes in your long-term memory, by creating stronger links between neurons in your hippocampus, the part of your brain associated with memory. A study based in northern England observed people singing in pubs and clubs, using it to come up with a list of the most “sing-along-able” songs. At the top of the list were ‘We are the Champions’ by Queen and ‘YMCA’ by the Village People, two songs with an undeniably catchy hook.

Songs also need to have a good rhythm if they are to be catchy and memorable. The belt and parabelt on the right side of our brain are involved in processing rhythms, and these have links to the motor cortex to get us tapping and moving along. Pitches are processed in the auditory cortex and prefrontal cortex, the latter of which is also involved in anticipation and creating expectations while listening. Therefore, the more interesting and varied the pitches within the hook of a song, the more it excites the prefrontal cortex and captures our attention. Furthermore, musicologists and psychologists have found that male vocalists, particularly those with higher voices who sing with some vocal effort, are more likely to incite singing along (though the ABBA ladies and Gloria Gaynor may beg to differ). They put this down to an intuitive part of our tribal subconscious that looks to men to lead us to battle, with higher and more forceful voices linked to more energy and purpose.

So, if the magic formula is simplicity, repetition, interesting melodies and higher male voices, it is no wonder that ‘Last Christmas’ still sticks around in our memories.

“Music is more than just sounds we listen to, but something far more powerful”

However, there is something even more special than this about the way that our brains store music, such that Alzheimer’s patients will remember songs they used to sing even after they’ve forgotten who they are. Those with Alzheimer’s have damage to their hippocampus and temporal lobe, which progressively diminishes their cognitive abilities and memory. Despite this, many patients continue to show a remarkable ability to remember music. Their musical memories are able to survive when their other memories are not. This indicates that there must be a “musical memory area” separate from the hippocampus and temporal lobe involved in music processing and memory.

A study looking into this phenomenon used healthy volunteers, playing them clips of well-known chart toppers, unknown songs and recently known songs. They found that the ventral pre-supplementary motor area and the caudal anterior cingulate gyrus were more active when listening to well-known songs to the extent that a computer could predict from the participants’ brain activity, whether or not they were familiar with the song. Further study on patients with Alzheimer’s found that this “musical memory area” was located in a part of the brain that was significantly less damaged by the disease. The shrinkage, decreased sugar uptake and build-up of sticky beta-amyloid plaque that causes brain cell death was much lower in this area, and thus musical memories were able to persist.

Music is more than just sounds we listen to, but something far more powerful. It brings us together, holds vivid and emotional memories, and takes us away from the stresses of life. Our brains have an innate capacity to remember music. Even when our other memories are gone, it is music that can remain.