The Music of the Metro

Paris is a unique city experience unlike any other I’ve partaken in. So many sites to visit, places to eat, districts to explore…how can one possibly get to them all? Simple: the Metro! Paris has an extensive metro system that covers any point you could ever want to visit. Atlanta may be fantastic in other respects, but the MARTA is definitely not set up for the burdens of massive public transportation. Riding the Metro daily to and from class was an entirely new process for me to get used to, from the rapidly closing doors to complete lack of personal space. Attached here is a picture of me in front of the station for the Balard train at the ACCENT center stop, Ledru Rollin.

Pictured above: the Balard Metro station as I wait for the next upcoming train three minutes away.

One of the first things I noticed about Metro riding was the efficiency; the doors closed so quickly after each person, I was shocked no one got stuck! As I got used to the train, I observed a noise that is played in front of every door right before it closes to alerts passengers that the door is closing. This noise is poignant and cutting, eliciting a harsh auditory reaction that informs passengers to stay clear of the area. As you hear it, you register that it is loud and unpleasant. What interested me so much is how this closing noise utilizes tonal dissonance to be more brash and effective. Attached below is an audio recording of the noise, taken during my morning commute (it may not open in Chrome, but it works in other web browsers).–mZPmrnmW2g42v8B_1V6CJ7B2vPkn5R/view?usp=sharing

This simple use of two tones causes such a visceral reaction for a reason; the frequencies of pitch and how they travel to the brain. Two pitches that are half or eight steps apart affect the same area of the basilar membrane, a structure located in the cochlea that is responsible for converting sound waves into nerve impulses that head to the brain. This joint stimulation results in beating (roughness in the basilar membrane) at a frequency that is determined by the difference between the two frequencies of the initial pitches (Johnson-Laird 2012). The clash between these almost-identical frequencies interact with one another to make a warbling, distorted sound.

This can be defined as a harmonically incongruous combination of notes, which is one that does not conform to the rules of harmony. The response to this in the brain is called the early right anterior negativity (ERAN); this event-related potential component occurs at an early latency, is prominent over anterior regions of the scalp, and tends to be lateralized to the right side. The amplitude of this response is modulated directly by attention and is more prominent in those with a familiarity towards music. An experiment was done observing harmonically incongruous chords in the context of a melodic sequence of chords and is shown in the figure below. Harmonically incongruous chords result in an attenuated response of neuronal firing when the tonal discord is in different positions (Positions 3, 5, 7) in the melodic phrase (Leino 2007). The hemispheric lateralization of the ERAN response is visible in the Position 3 example. In Position 7, the incongruous chord occurs at the end and elicits the strongest response and the greatest difference in neuronal firing rates.

Shows the difference in neuronal firing rates in specific areas of the brain during harmonically congruous and incongruous chords,

Of course, every individual has a different level of pitch identification. Absolute pitch refers to the phenomenon of identifying any pitch without given an external reference. Even during our pitch identification process, we activate the auditory cortex, prefrontal cortex, and certain parietal regions of the brain (Brauchli 2019); yet, we are not all as heavily invested in pitch as a musical function. Why is the ability to identify harmonic versus dissonant sounds in everyday life even important? Besides the tones used in music, language lends itself to a variety of colorful tones and variations in pitch. We use pitch in everyday conversation with specific inflection; for example, a rising pitch at the end of a sentence is often used to indicate a question. On the Metro, this understanding is important because it allows us to register a harmonically incongruous sound like the door closing and turn that into information: the train will soon close the doors. A small part of the everyday Parisian experience, yet an important one nonetheless. Maybe this is something you have yet to notice about the Metro experience, but it is fascinating regardless!

Aliyah Auerbach

Brauchli, C., Leipold, S., & Jäncke, L. (2019). Univariate and multivariate analyses of functional networks in absolute pitch. NeuroImage, 189, 241-247. doi:10.1016/j.neuroimage.2019.01.021

Jonhson-Laird, P. N., Kang, O. E., & Long, Y. C. (2012). On Musical Dissonance. Music Perception: An Interdisciplinary Journal, 30(1), 19-35.

Leino, S., Brattico, E., Tervaniemi, M., & Vuust, P. (2007). Representation of harmony rules in the human brain: Further evidence from event-related potentials. Brain Research, 1142, 169-177. doi:10.1016/j.brainres.2007.01.049

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