There are a number of mechanisms. Other people use a vibratory device called an electrolarynx which allows people to generate a recognizable but artificial voice. The best option is a voice prosthesis. By covering the airway in the neck with a finger, a patient is able to force air through the valve into the feeding tube and out the mouth. Relatively normal speech is achievable.
Chemotherapy refers to medication given, usually intravenously, to destroy cancer cells.
Since chemotherapy is usually given intravenously, it travels throughout the body and is able to destroy cancer cells throughout the body. Therefore, its primary role in cancer of the larynx is to destroy cancer cells that have spread throughout the body. In the last ten years, however, it has been shown that chemotherapy with radiation therapy is as effective as surgery and radiation therapy at curing large cancers of the larynx. This means that people with large cancers of the larynx have an opportunity to be cured of their cancer while saving their voice box. This is a very complicated question.