In June 2007, 2012 and 2014 Julian McGlashan and Cathrine Sadolin performed endoscopy studies and endoscopy/high speed studies in 2012 and 2014 at CVI in Copenhagen.

Twenty-one singers (ten males and eleven females) in 2007, thirteen singers (seven male and six females) in 2012, and sixteen singers (seven males and nine females) in 2014, a total of 32 singers (fifteen male and seventeen females), trained in the Complete Vocal Technique were recruited and asked to produce a sustained vowel in each of the four modes and then adding various sound colours to that that mode. Subsequently they were asked to alternate between the ‘clear’ mode and the mode with various sound colours.

30 subjects had pictures that we could analyse for this particular study, so the rest were excluded as they could either not tolerate the examination, did not perform the sound colours correctly, or the image quality was not adequate for interpretation.

Each singer was examined using an OTVS7 camera (Olympus) and ENFV2 videoscope (Keymed) coupled to the Laryngostrobe (Laryngograph) digital capture system. Laryngograph electrodes were positioned over the thyroid cartilages and an omnidirectional microphone placed at distance from the singer which allowed recordings at all levels of loudness. Also the ELG and acoustic signals were captured and analysed with the Speech Studio (Laryngograph) software program.

Each set of modes (with and without various sound colours) video images were analysed by Julian McGlashan and Cathrine Sadolin and the appearance and relationship between the key anatomical features was agreed by consensus and documented. The consistent features were identified and descriptive and explanatory text to aid pattern recognition.

The Laryngeal gestures are more to be seen as patterns of progression from mode to mode, rather than aboslutes. The progession in the patterns can be used as guidelines on how to identify the modes within each singer.

For the sound colours these are the parameters we looked at: the shape of the glottis, the position of the false cords, the anterior posterior narrowing, the shape of the pirriforma fossa, the hight of the larynx, the pharyngeal wall, the epiglottis and the arytenoid/cuneiform complex.

Not only did we look at what was changing between using the mode and the mode with various sound colours, we also looked at what was actually vibrating.


To get a better understanding of the laryngeal changes associated with sound colours and to examine the interaction of supraglottic vibration during intentional change of sound colours and vocal fold vibration.


We gave the various parts in the vocal tract levels in order to identify and specify on which levels the various changes take place. The levels also make it easier to communicate where the changes take place. On the videos from the footage only the first 3-4 levels are seen. For more info on the level, click here.


When we look at the video examples of the mode with dark and light sound colours, we see that the shape of the vocal tract is made bigger to make the sound colour darker; and smaller if the sound colour are to be lighter. This is done by changing the form and position of the epiglottic funnel, the larynx, the tongue, the mouth, the palate and the nasal passage. The position of the larynx (the larynx getting further away or closer to the camera) is the most obvious in this endoscopy recoding.


Changing of the sound colours can be done safely.

Notice that the waveform of the vocal mode is maintained during the change of sound colours.  This indicates that the vibrations of the vocal folds are unhindered and unaffected by the change of the sound colours. So the vocal folds are vibrating freely under the change of sound colours. This makes sense because the we know that the change of sound colours is taking place higher in the vocal tract and not on the 1st level (the level of the vocal folds).

In all the examples where we can see the vocal folds, or look at the laryngograph trace, there seems to be a resonably regular pattern, and there didn’t appear to be any evidence of the effect (or any additional noises) being produced in the vocal fold level.

There was evidence on endoscopy or from the Laryngograph of periodic vocal fold vibration.

It need a good technique to ensure accurate vocal mode setting done correctly and an intentional application of the effect.


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