Voice problems (dysphonia) affect one in 13 adults annually, causes a major impact on quality of life and livelihood and is a substantial healthcare burden. It is more common in women and in those with vocally demanding professions and the elderly. Forty percent of patients referred for assessment of a voice problem have Muscle Tension Dysphonia (MTD) as a cause brought on by an imbalance of breathing mechanism and/or uncontrolled tightness of the muscles of the voice box or throat. The main symptoms are hoarseness, abnormal pitch or loudness, variability in quality or control of the voice, throat discomfort or difficulty in using the voice such as being able to use a louder voice when needed, or a voice that fatigues with use with a consequent impact on quality of life. Traditionally there are six described recognisable patterns of MTD based on the presenting symptoms, voice quality and on appearance of the larynx (voice box) on examination with a video camera. Three types (MTD patterns I-III) are more related to ineffective voice use, also known as 'voice abuse' or 'voice misuse', while the other three types (MTD patterns IV-VI) have a predominantly psychological basis.

In the United Kingdom (UK), patients with persistent or unexplained hoarseness who are over the age of 45 are referred under the two-week wait (2WW) cancer referral process. In other cases, referral to an Ear, Nose and Throat (ENT) benign voice service is usually considered if the dysphonia persists for more than six weeks, if it has not improved with simple measures such as voice rest, reducing irritation to the vocal cords and drinking plenty of fluids (known as vocal hygiene advice) or it is impacting significantly on the patient's work or social life. In practice patients with MTD may come through both the 2WW and benign voice pathways.

A diagnosis of MTD is made by an ENT surgeon and/or Speech \& Language Therapist who has specialised in voice disorders (SLT-V) based on the history of the vocal complaint and by excluding an organic cause by examination of the patient's voice box (larynx) with a small flexible video camera passed through the nose. Treatment is with voice therapy given by a SLT-V. Voice therapy consists of two main types: Indirect Voice Therapy and Direct Voice Therapy and is guided by advice from professional organisations such as Royal College of Speech and Language Therapists Clinical Guidelines and the American Speech-Language-Hearing Association (ASHA) Clinical Practice Guideline: hoarseness (dysphonia). Indirect therapy consists of education, information, vocal hygiene, and stress management to encourage behavioural change. Direct therapy consists of establishing healthy voice production by rebalancing the three subsystems of voice production namely breathing (respiration), voice production (phonation) and more efficient use of resonance.

The aim of voice therapy is generally to (a) return the patient's voice to normal or as best as possible within the patient's anatomic and physiologic capabilities and (b) to satisfy the patient's occupational, social and emotional vocal needs and (c) promote habit changes that will ensure voice improvement will be maintained. Therapeutic goals should be specific and determined by the patient prior to therapy to empower the patient in shared decision making with the aim of improving motivation and compliance. In addition, the aim should be maximum improvement in the minimum time.

MTD is a mixed group of conditions with different patterns of presentation and numerous patient specific factors. In addition, Direct Voice Therapy is not just one treatment method and many SLT-Vs use a hierarchical approach, which focuses in the early stages on postural and relaxation techniques, followed by breathing exercises, voicing and resonance work with final consolidation and review. The techniques applied by a SLT-V are also dependent on abnormal findings on clinical examination the training and experience of the therapist and the response and engagement of the patient. Although having a large variety of techniques that can be used which can be tailored to the individual, Voice therapy has been portrayed as a "black box" and many recognised treatment regimens overlap in the treatment aims and therapeutic goals. This makes it difficult to determine why patients improve, which therapy tasks are most beneficial and for how long the tasks should be continued.

Another limitation of traditional Direct Voice Therapy can be that patients often have difficulty transferring the voice improvement on sustained vowels and during therapy sessions into conversational voice and day-to-day voice use. It is also recognised that patients do not always complete the therapy sessions in up to 18-65% of cases. Numerous reasons have been put forward for this, including clinician and clinic-related factors, gender, ethnicity, age, employment and perceived vocal severity, complex laryngeal diagnoses, additional medical problems, time commitment for treatment sessions or lack of rapid progress, adequate, if not complete, improvement in symptoms or failure to achieve goals. There is greater treatment satisfaction and likelihood of success if Direct Voice Therapy techniques are functionally orientated and have a more meaningful effect on quality of life with an emphasis on carryover activities into conversation so that it is more relevant to the patient's daily vocal demands. There is also increasing recognition that a patient may require more than one 'voice' to addresses the changing vocal needs (e.g., quiet talking, talking over noise, and yelling) in different environments.

Traditionally voice therapy has been given in a clinic environment face-to-face. However, with the onset of the Coronavirus (COVID-19) pandemic, Voice Therapy has almost entirely been given using telepractice via a video link. Prior to the COVID-19 pandemic, telepractice had been used by Speech and Language therapists mostly for geographical reasons and difficulties in patients' attending outpatient clinics. There are relatively few studies in its use for voice disorders and most studies on effectiveness have involved small cohorts of patients with a range of voice pathologies such as Parkinson's disease. There are few randomised controlled studies comparing face-to-face versus Telepractice and only one study of MTD patients using the same voice therapy technique (Flow phonation). This showed no significant difference in outcome between the two methods of delivery. Disadvantages of telepractice for voice therapy include generic problems with technology, patient environmental and cultural considerations, some instructional and practical issues with an inability to deliver more 'hands-on' techniques such as laryngeal manipulation. The Complete Vocal Technique (CVT) is pedagogic technique primarily used by singing teachers and vocal coaches to aid singers and actors produce the vocal sound and function that the performer requires. It has been used for over 35 years particularly in Europe and CVT practitioners (CVT-P) undergo an accredited 3-year training programme to achieve competency. It uses a hierarchical, systematic approach with terminology that is clearly defined and supported with scientific characterisation. It is based on four key building blocks enabling for example a singer to produce any vocal sound required in a healthy manner and regardless of genre of music. The first building block in CVT training is to ensure a healthy voice is produced by adopting the three overall principles: adequate support for the voice, use of a degree of twang ('necessary twang') and avoidance of jaw protrusion and tightening of the lips. Secondly one of four main vocal modes (Neutral, Curbing, Overdrive and Edge) is chosen which provides a set up for the larynx depending on the vocal requirement. These terms were introduced to avoid confusion with other more frequently used singing terms which lack precise definition. The choice of mode is determined by vocal demand (loudness, pitch range, vowel and genre 'norm' (vocal style) that is required: Neutral relates to normal conversational voice while the Curbing is a medium loud voice. Overdrive can be used for voice projection up to a shout loudness, while Edge can be used for a yelling and screaming quality. It would be expected that training in Neutral and Overdrive would allow good vocal function for most social situations for patients with MTD. The third element is to adjust the degree of sound colour (from dark to light) mostly achieved by lowering or raising the larynx and increasing or decreasing the pharyngeal space. The fourth element is to add specific vocal effects such as vibrato, ornamentation, distortion etc., which can be added once the first three have been achieved. In this way the precise sound required by the singer can be fashioned in any style or genre of music. The principles have been applied to training the speaking voice and provide a recipe for producing any desired voice quality for any environmental situation. A similar approach, that has not been widely adopted, has also been described whereby the aim is not to support the production of 'one voice', as is frequently the case with traditional SLT-VT, but to provide the patient with a range of 'new' voices to meet the patient's vocal needs.

Training programmes have been developed, using this methodology, to enable singers and singing teachers to improve, achieve vocal goals and overcome technical issues many of which are due to unintentional hyper-constrictive muscle activity within the larynx and vocal tract. CVT has also been applied to problems with the professional speaking voice and can help with reducing constriction and improved voice production and projection. Specific elements of CVT have also been packaged together in what is termed CVT Voice Therapy (CVT-VT). CVT-VT is used for singers and other performers presenting with acute vocal problems leading to hoarseness or loss of voice when time is of the essence in getting a vocalist back to professional voice use. Although widely used by CVT-Ps and published in several books it has not been formally evaluated.

The application of telepractice during the COVID-19 pandemic has also become a necessity in teaching singing and has been adopted by the Complete Vocal Institute (CVI) in Denmark where almost all tuition is now delivered on-line. Informal feedback from singers has been positive with many advantages (comfort of own home, reduction in cost, and no travel time) outweighing the disadvantages (some technical issues with audio/connection). It is likely a complete return to previous methods of delivery of SLT and CVT practice will not happen after the COVID-19 pandemic with the adoption of the new methods of service delivery for both.

In conclusion, the rationale for this Proof-of Concept study is to see whether an established pedagogic technique, CVT, which is used to train singers and performers with healthy voices and restore the voice when not functioning, can be used to treat patients with MTD and whether it offers advantages to traditional SLT-VT techniques. Many of the voice problems in performers and patients are due to faulty technique of voice production and are therefore similar to patients with MTD. In addition, the focus of CVT is not only to improve the voice and vocal function by reducing unhealthy throat constrictions but also allowing patients to develop the voice needed for the vocal requirement. Further, the terms and pedagogic process used in CVT are well defined and the theoretical framework on which it is built has been extensively investigated. The main questions are does it offer benefit, and how does it differ, from traditional SLT-VT methods and could it be a useful additional tool for SLT-VTs in the management of MTD?