The term 'Symphonic Silence Symbol' refers to the musical notation of a REST, which is represented by a four-letter word: REST. A REST is a period of silence in a piece of music, and is indicated by a symbol that looks like an upside-down hat. It is used to indicate a pause in the music, and can be of any length depending on the type of REST used. The most common type of REST is a quarter REST, which is equal to one beat in 4/4 time.