How the Brain Processes Music
Hearing music is actually the result of a series of complex steps that convert sound waves in the air to electrical signals in the brain. Sound waves first enter the brain as vibrations through the cochlear nuclei, located in each ear. Cochlear nuclei are lined with tiny hair cells tuned to different frequencies – some high, some low, with a full range in between. These hair cells convert the air vibrations into electrical impulses that are then carried to auditory centers in the brain stem. These auditory centers are part of the central auditory nervous system (CANS), which includes nerve fibers and nuclei that extend from the brain stem through the midbrain to the cortex.
These musical impulses then move from the brain stem to the cerebellum, located just above the brain stem. It’s the cerebellum, with its emphasis on motor control, coordination, precision, and timing that locks us into a rhythm. Tapping, drumming, walking, or any other kind of movement in time with the music involves the cerebellum’s timing circuits.
The neural signals then move up to the auditory cortex, which, amazingly, is laid out in pitch order from low notes to high notes, similar to a piano keyboard. They then travel to the hippocampus, forming and retrieving memories, before moving on to parts of the frontal lobe. The frontal lobe is responsible for executive functions: cognitive skills such as planning, organizing, initiating, and thinking – all skills we need in order to move along to the music, sing, dance, or play an instrument.
The limbic system also becomes activated, specifically the amygdala, which is the core of emotional processing. As we all know, music can be very emotional. It’s commonly understood that a 2:1 ratio (an octave) and a 3:2 ratio (a perfect fifth) give us the most pleasure. But why? Scientists found that it has to do with rhythmically consistent firing patterns in the auditory neurons – a result of how our brains convert tones to electrical impulses. When two tones are picked up by two different neurons, converted to electrical impulses and combined at the same time, it results in regular pulses going to the brain. We call this harmony and our brains love the regularity. When two tones from the receiving neurons are converted to electrical impulses at different times, it creates irregularly spaced pulsing. We call this dissonance, and while it is not as comfortable for the brain, it does challenge the brain to work to make sense of it.
There are many steps and a multitude of brain processes all working at lightening speed to give us a complete musical experience and a full brain workout. This happens every time we experience music!
