The triangle is a percussion instrument of the idiophone family. It is usually made of steel but can be made of other metal types. As its name suggests, it is triangular in shape, though the shape is left open so that the instrument can vibrate and produce its sound when struck. The triangle is traditionally suspended on a piece of string or line, allowing it vibrate freely. Despite its apparent simplicity, the triangle can be quite challenging to play, and most classical pieces calling for it are demanding, requiring extremely rapid, controlled strikes.
The triangle produces a bright, ringing, chime-like sound when struck.
The triangle has been used in classical music since around the mid 18th century.