Physical aspects of Timbre Contrasts
“Voice production includes three major levels. The vibrating force is the exhaled air, the vibrators are the vocal folds and the resonance is imparted by […] the vocal tract”1 .
Vocal tract includes the areas from the glottis to the lips (see diagram). “In singing, the sound is generated by the vocal folds and resonated in the chamber of air defined by the vocal tract”2 .
Timbral contrasts are achieved by any adjustment (little to extreme) of any of these levels. In detail, they are mainly achieved by “using the structures of the vocal tract in different ways to control and shape moving air”3
The specialists Jerold Edmondson and John Esling with their laryngoscopic research concluded in six major valves that control the posture of the lower vocal tract and are responsible -among others- for voicing, the quality of voicing , the differences in phonation type for vocal register and the tone4.
More simplified for the sake of a brief exploration, the main mechanisms that we can voluntary control for shaping the desired quality of the voice/timbre are:
a. Vocal folds
Vocal folds have the ability of rapid adjustments. The vocalist can control the vocal folds changing the pitch and their contact quality. As the pitch rises and resonance moves to "head voice", vocal folds are stretched and eventually become thinner. On the other hand, as the pitch gets lower they become shorter and thicker, causing a deeper and louder sound.
The vocalist can control the muscle mass during their contact “bringing more chest resonance up into the head voice than usual” such as in “belting” technique5.
Adding more muscle mass while already resonating on the "chest voice" transforms the timbre into a deeper sound, such as Lisa Gerard does in Sanvean, or I do during the Ancient Sibyl's voice in SHE...NEN.
b. Laryngeal raising or lowering
The rise of the larynx is felt when we swallow. A relaxed larynx is in a low position. It can voluntary be lowered (as it happens usually in healthy classical singing, in low pitch and throat singing) or raised.
A raised larynx creates a thiner or “pressed phonation […] usually more efficient aerodynamically and acoustically”6.
c. Pharyngeal constriction or narrowing and false folds vibration
Pharynx gives the space for the front and back movement of the tongue7 and it is the first resonating chamber in the vocal tract8.
Its little to extreme constriction/narrowing (felt when we swallow or throw up) creates different timbres and potentially brings false folds closer causing their, like in Tibetan Monks/ Mongolian throat singing.
d. Soft palate movements
The lift or rise of the soft palate closes the access to the nasal cavity, increases the vertical space of the pharynx9 and expands the oral cavity, allowing different kind of resonances and timbres such as nasal.
e. Tongue position, oral cavity and lips
“The eight muscles of the tongue are capable of complex and independent movement”10. Tongue forms vowels and consonants of different quality, with the cooperation of the lips and cheeks. It absorbs harmonics or creates and controls others, such as overtones.
The buccinator muscles (forming the inside of the cheeks) and the lip (orbicularis oris) muscles can shorten or lengthen the oral cavity and create different spaces/chambers. For example, a wide lateral opening brings a brighter, shallower and spread sound11.
Throughout our lives we use unconsciously these mechanisms to talk, sing, imitate sounds or nuances and express in different ways. Voice is an instrument we cannot completely see or feel, but the improvement of technology with the examples of Χ-ray, MRI and Laryngoscopy, bring scientific conclusions that help the imagination of vocalists regarding awareness, kinaesthesia and understanding of the vocal mechanism.
Laryngoscopy of various extended techniques (edited video for research purposes)
Visible adjustments of the vocal folds,false folds and pharyngeal constriction.
