Belting (or vocal belting) is a specific technique of singing by which a singer mixes in the proper proportions, their lower and upper resonances; resulting a sound that resembles yelling but is actually a controlled, sustained phonation. 'Belting' is sometimes described as 'high chest voice' but this is technically incorrect, and if done incorrectly can potentially be damaging for the voice. It is often described as a vocal register, although this is also technically incorrect; it is rather a descriptive for the use of a register. Singers can use belting to convey heightened emotional states.
"Chest register" is the lowest register of the singing voice, produced by dominant use of the thyroarytenoid muscle. The term "belt" is sometimes mistakenly described as the use of chest voice in the higher part of the voice. The chest voice is a general term for the sound and muscular functions of the speaking voice, singing in the lower range, and the voice used to shout. Each of those functions requires a thicker closure of the vocal folds and the support of the muscles surrounding them. The term "chest voice" is therefore a misunderstanding when it describes muscular work in the chest-area of the body, or a resonance therein. Proper production of the belt voice, according to some vocal methods, involves minimizing tension in the throat and a change of typical placement of the voice sound in the mouth, bringing it forward into the hard palate, although techniques vary by pedagogical style.
It is possible to learn classical vocal methods like bel canto and also to be able to belt; in fact, many roles now require it. Vocalists trained in a wide berth of styles describe vastly varying experiences in learning belt technique. Some claim that it comes naturally, while others struggle to access chest register other than while speaking. Style of music does not seem to be a related factor, other than in a singer's exposure to material.
Belt technique requires muscle coordination not readily used in classically trained singers as the thyroarytenoid muscle is dominant (as opposed to head register singing where the cricothyroid muscle is dominant), which may be why some opera singers find learning to belt challenging.
In order to increase range and stamina, one must practice, however physiology and physical limitations should always be taken into consideration in a realistic approach. Since belting can be harsh on the vocal mechanism if care is not taken, supervision by a teacher experienced in working with belters is recommended in order to avoid developing lifelong pathologies that could be otherwise avoided. Others recommend repeatedly attempting to hit a note in a melody line, or by using vocalise. Many commercial learn-to-sing packages have a set of scales to sing along to as their main offering, with which the purchaser must practice often to see improvement. However, these packages do not offer a user feedback in terms of posture, breath support, muscular constriction, or any assistance with difficulties that a singer may encounter. Since this is not a separate instrument but a part of the human body, care must be taken not to damage it in a way that may later require surgery, so learning to belt without proper supervision is not advised.
'Belters', as well as other singers, should balance their registers and develop a strong head voice, in order to facilitate muscular coordination and avoid constriction. Some singers, particularly if their chest registers are underdeveloped, find that after a period of time focusing on the belt, the head voice will have improved. Likewise, for a singer with an underdeveloped head register, after a period of time focusing on the head voice, the belt may be found to have improved.
There are many explanations as to how the belting voice quality is produced. Under a scope, the vocal folds visibly shorten and thicken, and they undulate along more of their vertical surface area than in head register when a smaller segment of their edge must undulate to produce sound.
One researcher, Jo Estill, has conducted research on the belting voice, and describes the belting voice as an extremely muscular and physical way of singing. When observing the vocal tract and torso of singers, while belting, Estill observed:
Belting without proper coordination can lead to constriction of the muscles surrounding the vocal mechanism. Constriction can consequently lead to vocal deterioration. Correct use of the technique and, most importantly, retraction of the ventricular folds while singing is vital to safe belting. Without proper training in retraction, belting can indeed cause trauma to the vocal folds that requires the immediate attention of a doctor.
Some proponents of belting say that it is a "soft yell," and if produced properly it can be healthy. It does not require straining and they say it is not damaging to the voice. On the other hand, it is thought by some that belting will produce nodules. This may be true if belting is done incorrectly. Many in the musical theater industry like to quip, "belting is not bad; bad belting is bad."
As for the physiological and acoustical features of the metallic voices, a master's thesis has drawn the following conclusions: