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Apparently vocal cords don't "zip" up...

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Sorry if this has already been discussed but after seeing some youtube videos of singers vocal cords in use it appears that the cords remain parallel to one another while singing but just get longer and shorter depending on the pitch. Here's a video example...

Please correct me if I'm wrong by the way. If indeed the cords don't "zip up" then what is really happening while bridging?

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Yes as a visualization it can help to think that the folds "zip up".

Thus there are no scientific proof that they do "zip". And actually the ones that made this popular like SLS doesn't really use that anymore. It was popular once but now it is sort of outdated.

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you know its funny because thats what the latest research points to apparently, though it seem that the folds may " zip" up for the whistle voice. i have seen a couple of vids though where it looks as if some "zipping" may be taking place.

before the guy flips/breaks into falsetto it looks like there may be some "zipping"

steven tyler high notes at 1:05 also looks like "zipping"

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you know its funny because thats what the latest research points to apparently, though it seem that the folds may " zip" up for the whistle voice. i have seen a couple of vids though where it looks as if some "zipping" may be taking place.

before the guy flips/breaks into falsetto it looks like there may be some "zipping"

steven tyler high notes at 1:05 also looks like "zipping"

Centre: The idea of 'zipping' of the vocal process is an interesting one to research. Some of the first laryngeal pictures which seem to indicate this effect come from Brodnitz. Unfortunately, the pictures he took were still photographs, and as we know, the vibrating vocal bands are in rapid motion.

I've spent a bit of time looking into this over the years, and the best (most plausible/rational/justifiable, from my perspective) explanation I have seen is this: When singing with firmly adducted arytenoid cartileges (which are at the posterior (back) end of the vocal process) the part of the glottis that opens first in the open/close cycle is the anterior (forward) part. In very rapid succession, the mucosal wave extends the glottal opening posteriorly for the first half of the cyle, and then the glottis shuts in the 2nd half. Importantly, the rapidity of the shutting motion is a major determinant of the harmonic content of the phonated tone.

If the glottal open motion is watched in very slo-mo, it looks rather like the 'completely zipped up glottis' is 'unzipped' from the front to open it. :-)

The extent to which the glottal opening extends backward during the first half of the cycle has somewhat to do with the tissue elasticities of the vocal process itself. When the singer has well-balanced registration, the vocal process has been progressively stretched (by the action of the crico-thyroid muscles responding to the higher pitched mental image, resulting in thyroid cartilege tilt) as the singer ascends the scale.

For some singers, for whom, in the lower ranges, the glottis opens well from front to back, including almost all of the length of the vocal process, there is a pitch point where the open motion cannot proceed all the way to the back of the vocal process before the closing motion begins. For such singers, if a scale is watched which crosses this transition, at normal speeds it appears that the glottis is 'zipping' up. What is happening is that it is no longer opening as far posteriorly during each cycle as it did on the lower notes.

That's what makes sense to me. I hope this helps in our discussion.

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yes, usually the very simple explanation for the zipping vocal folds is like fretting a string on a guitar, thus reducing the vibrating length. what is interesting from the two vids i posted is the steve tyler one looks like how it is described/theorized to happen I.E. the zipping, dampening or fretting happening at the front (leaving a smaller portion or length of cord to continue the open/close cycle) but the first one of the guy doing the slide looks like a zipping from both back and front before he flips into falsetto. maybe its a trick of light shimmering on mucous or something....:lol:

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... usually the very simple explanation for the zipping vocal folds is like fretting a string on a guitar, thus reducing the vibrating length. what is interesting from the two vids i posted is the steve tyler one looks like how it is described/theorized to happen I.E. the zipping, dampening or fretting happening at the front (leaving a smaller portion or length of cord to continue the open/close cycle) but the first one of the guy doing the slide looks like a zipping from both back and front before he flips into falsetto. maybe its a trick of light shimmering on mucous or something....:lol:

Centre: While apt as a visualization, I think the comparison of vocal process 'zipping' to fretting a string on a guitar leaves out pertinent details of vocal fold motion. In the case of the guitar, the action of fretting the string shortens the length of the string allowed to vibrate, without affecting the cross-section of the string or its tension. The change in note is directly caused by the shortened vibrating length, and no other appreciable factors.

In singing, the fundamental of the phonated tone is the result of a complex relationship between length and stiffness of the vocal fold tissues, mostly influenced by the muscle interactions between the those which shorten/thicken (the Thyro-arytenoids (TAs) & vocalis) and those which lengthen/stretch (CTs). There are no muscular actions within the larynx which are analogous to pressing of the guitar string. If what is observed as 'zipping' occurs in a voice (and this is by no means universal amongst singers,) its the natural byproduct of changes in vocal fold motion directly due to stretching in the presence of various engagement of the TAs, and an appropriate level of breath energy.

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yes the fretting guitar string analogy is only really meant to serve as a ultra simplified visualization to the zipping cords theory. you summed it up best when you said....

"The extent to which the glottal opening extends backward during the first half of the cycle has somewhat to do with the tissue elasticities of the vocal process itself. When the singer has well-balanced registration, the vocal process has been progressively stretched (by the action of the crico-thyroid muscles responding to the higher pitched mental image, resulting in thyroid cartilege tilt) as the singer ascends the scale.

For some singers, for whom, in the lower ranges, the glottis opens well from front to back, including almost all of the length of the vocal process, there is a pitch point where the open motion cannot proceed all the way to the back of the vocal process before the closing motion begins. For such singers, if a scale is watched which crosses this transition, at normal speeds it appears that the glottis is 'zipping' up. What is happening is that it is no longer opening as far posteriorly during each cycle as it did on the lower notes."

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If you'll pardon an engineer stepping in here, there is one other point regarding what you see on a video of the vocal folds:

Almost all of these videos have been made with a stroboscope -- a brief-flashing very-bright white light (like the MCs use for dances!) that is such a short pulse that it "stops" the folds in their tracks -- like a flash photo of a football quarterback kicking the ball into play. The difference is that the stroboscope flashes over and over again, at a period that can be selected by the photographer. Doctors have been using strobes for years to examine the folds for polyps and nodules and other anomalies that would just be a blur if seen with continuous white light.

If the VF are cycling at 220 Hz (A below Middle C), and if the doctor wants to "stop" the motion so she can carefully examine how a lesion behaves -- as if hard and dry, or as if floppy and wet -- then she would set the strobe to 220 pulses per second. Each time it flashed, the picture would show the folds in exactly the same position (assuming the singer isn't using any vibrato or tremolo) and the shape of the polyp would either remain the same or wobble around irregularly.

To get an impression of how the folds operate through their entire cycle, she could set the strobe to 219 Hz, and that way each picture frame would be 1/219th of a second later, while the folds continued at 220. Each frame would be delayed by this slight interval, and over the period of one full second it would build up an apparent 'movie' of the entire open-close-open again cycle. It would look like the folds are oscillating at 1.0 Hz, even though they aren't -- as your ear could easily tell.

Often these stop-action slow-motion videos are backed up with real-time audio on the recordings.

Until very recently, it's been virtually impossible to use true high-speed cameras to actually take pictures so frequently that a true sequence of 220 frames could be recorded. You can do this on a jet engine, but not on a living set of vocal folds, because the amount of light, integrated (added up) over the full period would broil -- yes, broil! -- the vocal folds. (If you think smoking is bad . . . ) So, many of the videos we see are actually strobe images. If the strobe is set by the operator to reveal a particular motion pattern of interest, then -- for example -- we could see the folds appearing to "zip" or "unzip" -- to open only partially -- when in fact they may be opening fully but only during the dark cycle.

An interim way to see VF behavior in real time is using the video kymograph (http://www.kymography.com/) but this device only shows the motion of a single point along the folds. If the point is chosen near where you're missing the open behavior, it will reveal that behavior in a measurable way. But it's just not the same as viewing the entire vocal fold area.

In "whistle" register, the vocal folds aren't even cycling. This is a form of whispering, but with a single fixed opening at one end of the immobilized folds forming the jet of a whistle -- like blowing a stream of air between your two front teeth, or puckering your lips into a tiny "OO" shape and then blowing out through them. Try whispering a very loud "EE" sound, and you'll be in the right arena. The pitch results from shedding vortices spinning one after the other -- left and right -- up into your vocal tract. If I remember right, the epiglottis can be somewhat tuned to reinforce and filter these passages, creating its own formant at an abnormally high pitch.

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