The term 'PERFORMED BY A CHOIR' can be summarized by the solution 'SUNG', which is a 4-letter word. Singing is an activity that has been around for centuries, and it is often done in groups, such as choirs. Choirs are typically composed of singers who perform together in harmony to create a beautiful sound. Singing in a choir is a popular form of performance, and it is often used to express emotion or to tell stories.