Silence is a piece of music that can be unlocked when no one is around you. This includes NPCs. Silence cannot only be heard on RuneScape. It can also be heard in real life e.g when you are in the middle of an empty street, or when all is quiet and peaceful. The Silence piece of music does not require a speaker to be heard. Infact, it cannot be heard at all. A minority (yes, minority) of players consider Silence a really bad piece of music.