Intentional Distorted Voice Techniques: a challenge for the concept of Vocal Registers

This study aims to explore how intentional distorted voice techniques (IDVT) challenge the concept of vocal registers in contemporary singing. IDVT, popularly known as vocal drives in Brazil and South America, have been defined as a “break in the fundamental frequency of the voice”, or “a break in the continuity of airflow”. This break may be generated by the supraglottis, glottis, or a combination of both (Coelho, 2014; Silva, 2015; Güths; Coelho; Rolim, 2021). A vocal register, on the other hand, is defined as a:

“totally a laryngeal event; it consists of a series or range of consecutive voice frequencies which can be produced with nearly identical phonatory quality; that there will be little overlap in fundamental frequency between adjacent registers, and that the operational definition of a register must depend on supporting perceptual, acoustic, physiologic and aerodynamic evidence” (Hollien, 1974, pg. 125).

Several authors state that vocal registers lack precise definitions (Sundberg, 2018; Güths; Coelho; Rolim, 2021; Güths; Coelho, 2023). Güths and Coelho (2023) emphasize that vocal registers were developed in a historical period when technological resources for investigating laryngeal physiology were scarce. Also, the goal was to develop pedagogical tools for singing rather than exploring the full physiological scope of the human voice. This is one of the reasons why vocal registers are inefficient in explaining esophageal voice, for example — what is the register of an esophageal voice?

The concept of vocal registers is also challenged by glottal IDVTs (g-IDVTs). Güths, Rolim and Coelho (2021) analyzed nasolaringoscopic images and acoustic spectrography of two g-IDVTs used by trained rock singers in Brazil. They observed that the opening of the posterior third of the glottis serves as a protective maneuver for the vocal folds and the mobilization of the mucosa was observed in this region as well as in the arytenoids region. The activation of the thyroarytenoid muscle (TA) was observed. According to Hirano (1988, pg. 59), “the vocal register is basically regulated by the ratio of the vocalis and cricothyroid activities” and TA activation is greater in chest register and decreases in higher registers. However, the author adds that “the CT activity does not differ very much among the three registers” which might suggest the TA as the main responsible for the changing register’s perceptual effect. Consequently, both g-IDVTs could be classified as in the “chest” register, even though they differ in physiology, perceptual, acoustic and aerodynamic levels.

In conclusion, phenomena such as g-IDVTs perhaps might be evidence that the human voice is not divided into vocal registers.