For centuries the art of singing has been shrouded in mystery. Teachers and singers have had to rely more on sensation and guesswork, as they did not have the knowledge or understanding of how the voice functions. Recent developments in voice science have given us a clearer functional understanding of how the voice, body and mind function during singing.
Historically, singers were taught they all had two voices, with a passage, or bridge, between them. The first emanated from their chest referred to as chest voice, the historical Italian term was ‘voce di petto’. The second emanated from their head and was referred to as head voice or ‘voce di testa’. Between these two registers was a connecting bridge which the Italians referred to as the pasaggio. Whilst these terms may have coincided with some of the subjective sensations singers feel, the head and chest are NOT resonating cavities for singing. Sometimes singers may feel resonance sensations in those areas due to bone conduction, but to really understand what constitutes registers in singing we have to dig a little deeper and turn to voice science.
To understand registers we must first understand the mechanism that is responsible for them: the vocal folds. The vibrating vocal folds or ‘cords’ are the sound source. Put simply, they are responsible for chopping up the pressurised air stream which creates sound. Whilst resonance and articulation play an important role in shaping the raw acoustic material from the sound source, the vocal folds themselves also play a huge part in determining the register and timbral characteristics of a sung note.
The vocal folds are a multilayered structure of tissues (imagine a trifle!) They function as two main layers, the cover (cream & custard) and the body (jelly, sponge & fruit). Whilst the body and cover are anatomically connected, they behave as two independent layers during sound production.
I refer to the mechanical behaviour of the vocal folds in different registers as Laryngeal Mechanisms, because the vocal folds change their behaviour (vibration pattern) in each mechanism or laryngeal register. Nathalie Heinrich (one of my PhD supervisors) has given us a fantastic model to easily understand this complex behaviour of the vocal folds, and named her model Laryngeal Mechanisms. Heinrich’s model describes how the body and cover of the vocal folds behave when producing different laryngeal registers.
Nathalie has identified four main scientific laryngeal mechanisms: M0, M1, M2 and M3. Giving them a number helps avoid previous historical associations which may have not been correct. The four laryngeal mechanics are classified as follows:
M0 – where both the body and cover are loose
M1 – where the body and cover vibrate
M2 – where the body is no longer involved in the vibration, described as ‘decoupling in the layered structure of the vocal folds’.
M3 – where the vocal folds are very thin and very tightly stretched; with only the cover involved in the vibration, often with incomplete vocal fold closure.
Historically, these registers were referred to by various names including:
M0 – vocal fold fry, slack folds or strohbass
M1 – modal, thick folds, chest voice, heavy mechanism
M2 – thin folds, light mechanism, loft, head voice (women), falsetto (in men)
M3 – Whistle register, stiff folds
This model allows us to understand and train specific laryngeal mechanisms (registers) from a solid basis of how they are physiologically produced.
Now we can turn our attention to acoustic registers. Once the raw material from the vocal folds has been created, it travels up through the vocal tract and out of the mouth. The vocal tract plays an important role in shaping the raw acoustic material provided by the vocal folds into consonants and vowels; acoustic vocal timbre is also shaped in the vocal tract. We refer to this as acoustic registration. We need both laryngeal and acoustic registration to truly understand and control singing registers. We know through modern research that acoustic registration is a vital component in negotiating a singer’s range comfortably.