Swing Jazz and Neural Oscillations




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If you’ve ever listened to swing music, you may have noticed that the notes aren’t evenly spaced — there’s usually a little bit of extra time between eighth-notes that results in the characteristic “swinging” feel of the music. Whether you like swing or not, you can’t deny that for many people, this unevenness has a certain aesthetic appeal. But why is this noticeable? Why don’t we just attune to the adjusted beat?

A recent study shed some light on this very topic in a fascinating use of neuroimaging. The focus of the article was non-metrical rhythms; “metrical” meaning evenly spaced and on an integer ratio. For example, 4/4 time is metrical, as is a 1:3 ratio (which signifies a note being played at the beginning of a measure, 33% of the way through a the measure, and 67% of the way through the measure). A non-metrical rhythm, then, is something like 1:2.89.

The researchers used an EEG component — the omission elicited potential (OEP) — to see when their subjects predicted a note while listening to music. The OEP is a positive deflection seen when the brain is expecting a stimulus, but doesn’t perceive it. By analyzing the time at which the OEP occurs, it can be determined when the stimulus was expected. The researchers played beats for participants that included a 33% subdivision (1:3), a 43% subdivision, and a 53% subdivision.

What they found was that rhythms are regularized by the brain, meaning that participants expected the notes to be closer to an integer ratio than they actually were. Specifically, when the 33% stimulus was omitted from a trial, an OEP occurred around the 33% mark, or very near to when that note would have been played had it not been omitted. However, when the 43% note was omitted, the OEP occurred later than 43% — closer to the 1:2 mark. The same happened when the 53% stimulus was omitted, only this time the OEP came before the note would have been played, also moving closer to the 50% subdivision.

Although the brain doesn’t adjust its expectations all the way to a metrical rhythm (i.e., the OEP did not occur exactly at the 50% mark), it does seem to regularize non-metrical patterns to a certain degree, creating violations of our expectations with deviations from the expected pattern. Interestingly, expectations are not adjusted to the nearest metrical possibility, but to the nearest major one. For example, a 2/5 time would place a note closer to the 43% subdivision, but this is a strange and uncommon rhythm, so it was not the target of regularization.

The authors explain the creation of these expectations as effects of neural oscillatory mechanisms, one of the methods posited to perform temporal measurement in the brain. These oscillations coordinate and help us keep time, and the form the expectations that, when violated, result in the OEP.

Is it the violations of these assumptions that creates the appeal of swing music and other genres that use unusual timing and time signatures, such as other forms of jazz, indie, and metalcore? It’s hard to say. But it seems that our brains — at least for those of us who have grown up with Western music, which generally uses a specific timing system, do have a specific reaction to this musical property. Exactly what this finding means for neuroscience and for music is yet to be seen.

References

Motz BA, Erickson MA, & Hetrick WP (2013). To the beat of your own drum: cortical regularization of non-integer ratio rhythms toward metrical patterns. Brain and cognition, 81 (3), 329-36 PMID: 23434916

Image via Everett Collection / Shutterstock.

  • Mandy

    I love finding out things like this, shows why we like what we like and it’s not just coincidence. Every action has an equal and opposite reaction and this is the reason I love swing :)

  • Matt “Musician X” Falter

    That is a very interesting article and a great worthwhile endeavor by those neuroscientists. However, if they look into the already well established research of Milford Graves, then they would realize that swing appeals to us because it has a rhythm that is more harmonious with us biologically, particularly in relation to the heart which has many electrical signals with both metric and non-metric subdivisions and the resulting heartbeat which has a subdivision like that of the golden ratio, or 3/5. You will notice that much of the music of New Orleans and that of Swing have that subdivision. Actually, much music around the globe has that 3/5 feeling to it. It is, in fact, a global/human tradition.

    I would be curious what their results would be had they tried a 3/5 subdivision, and if they were to try it at faster and slower speeds (because the slower the tempo, the stranger the 3/5 feels). I imagine they would get mixed results depending on what each listener was accustomed to.

    This article, pondering the significance of the tests that were performed, ponders whether swung 8th notes are “unexpected” to the listener of whom it appeals, but the truth is that it is quite expected to those who like it and are culturally accustomed to it. In the test that was performed, if they had used the 43% subdivision with someone who had been listening to music with 43% subdivisions their whole life, then the OEC would occur at 43%. It’s that simple. If they were to try it on me (or someone from West Africa), they would get an OEC reading at around 44% or 45% because there is a very common African rhythm to which I am well accustomed that is a lilted triplet. It has a 4/9 subdivision followed by a 2/3 subdivision, hence, a “lilted” triplet.

    As an American who plays West African music quite well, I have seen countless Americans try and fail to play West African rhythms with that 4/9 subdivision (some of them very talented musicians). They will change the 4/9 subdivision to a 1/2 subdivision and change the 2/3 subdivision to a 3/4 subdivision because that is what they are used to hearing. But it doesn’t matter if an American can read music or not, they will “Westernize” it into simpler metric subdivisions because that is what they are accustomed to hearing and so the electrical signals from their brains cause their hands to move with those simpler subdivisions.

    Those who are more clever among the classically trained will keep the 2/3 subdivision but still change the 4/9 subdivision to 1/2, because the 1/2 followed by 2/3 is something they have become accustomed to in classical music. But it doesn’t matter if they are knowledgeable of rhythmic theory and I explain it to them in any of several ways using Western context (one example: a quarter-note-triplet followed by a quarter note in 3/4 time, then the bar is repeated over and over, then sped up or “shrunk down” into one beat). It all fails because the electrical signals from their brains can not send the signals to their hands with rhythms that have not been engrained in their brains first.

    And don’t get me started on Brazilian music … it has extremely non-metric subdivisions. If they were to conduct the 43% test on someone from Brazil, the OEC would read at about 40 to 42%. That’s a whole other discussion.

    • http://brainblogger.com Daniel Albright, MA

      You bring up a lot of really good points here, Matt! I’ll definitely have to look into Milford Graves—I’m not familiar with his work, but it sounds really interesting.

      One of the things that you said caught my eye: “it is quite expected to those who like it and are culturally accustomed to it.” I definitely agree with you on the cultural part; it’s quite likely that people who have been exposed from a very young age to systems of music that contain certain time signatures or other features would show an OEP closer to the traditional placement of a note than listeners who grew up with Western (or any other system) of music.

      However, what really piqued my curiosity was the idea of aficionados of a certain kind of music adjusting their expectations, even to patterns that violate the systems of music they grew up with. I’ve been reading a bit about brain plasticity lately, and I think there’s something work investigating there—how long do people have to be exposed to a non-standard system for their neural oscillations to regularize to it? Will they then start showing OEPs to more standard variations? Do children adjust more rapidly than adults?

      I think all of these are very good questions. Thanks for contributing—I really enjoyed your comment!

      • Matt “Musician X” Falter

        Fascinating thoughts, Daniel! We make a good team :)

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  • gee

    SYNCOPATION IS SYNC’D WHEN IT IS ONE FULL BEAT DIVIDED INTO A 1/3 2/3’S RATIO. AS A MEMBER OF THE BAND I WAS TAUGHT THAT THIS TYPE OF RATIO WAS VERY DIFFICULT TO PLAY…IT SEEMED TO ME TO BE TRUE. I WORKED HARD AT GETTING IT DOWN. NOW I NOTICE HOW THERE ARE THOSE SYNCOPATION CHEATERS WHO PLAY A 3/4, 1/4 RATIO.WHICH IN MY MIND IS MUCH EASIER TO PLAY. AND ALL OF THIS EXPLAINS TO ME WHY SOME SWINGIN’ BLUES SOUNDS ARE SOON TO BORE AND OTHERS ARE SWINGIN’AND GROOVY AND KEEP IT COMIN’ LOVE THOSE MOZART HONEY-STUNG BLUES,JIVE-CATS.

Daniel Albright, MA, PhD (c)

Daniel Albright, MA, is a PhD student at the University of Reading, studying the lateralization of linguistically mediated event perception. He received his masters in linguistics from the University of Colorado-Boulder. Get in touch with him at www.dannalbright.com or on Twitter at @dann_albright.
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