The act of listening to music starts in the aural region of the brain and moves through the brain stem and cerebellum and into both sides of the brain, according to Daniel Levitin in his book, "This is Your Brain on Music." The memory center of the brain, or hippocampus, plus the parts of the frontal lobe, become active trying to associate music with forms, styles or melodies it has already heard.
Levitin also explains that the cerebellum's timekeepers or timing circuits are awakened when people try to keep time with the rhythm of music. This includes the durations of notes as well as how they are grouped into units. Tempo is also considered here: whether the music is fast, slow or medium. The brain tends to expect events in music based on what it has heard before, so unusual events happening in music add excitement. An example of this would be syncopation, where a note starts ahead of the beat.
The frontal lobes and the motor cortex in the parietal lobe (underneath the top of the head) are called upon when performing music. Instrumentalists, singers and conductors all use the frontal lobes that plan movements and behavior. The motor cortex and sensory cortex give the performer the tactile feelings that assure them that they are hitting the right keys or waving a baton correctly.
The brain interprets music based on what it expects to hear. When the brain hears something unexpected or it is forced to wait for something it anticipates (such as a harmonic resolution), tension and excitement are created. According to Robert Jourdain in "Music, The Brain, and Ecstasy," the brain is so used to the conventions of music that it will expect them even if it has heard and processed the unexpected moments in a piece of music already.
Classical music is used effectively in the treatment of certain neurological disorders such as depression, autism and Parkinson's Disease. Parkinson's patients, according to Jourdain, respond to the continuous flow of music. According to EEG (electroencephalogram) studies, patients' debilitating twitching and halting brain waves seem to smooth toward normal when their favorite music is played.