An emollient is a compound that reduces swelling. Slippery elm helps to reduce the pain of a sore throat by reducing the swollen glands commonly associated with sore throats.
The word "demulcent" comes from the Latin word "demulcere," which means to caress. A delmulcent is something that soothes or caresses the surface of a mucous membrane, relieving irritation and inflammation. Slippery elm acts as a demulcent in the throat and nasal passages to relieve irritation, making singing easier.
When a lozenge of slippery elm bark is placed in the mouth, the moistened powder creates a mucilage that soothes the irritation. A tea made of slippery elm bark also provides the mucilaginous properties that coat the throat.