Triangles are made from a variety of metals including aluminum, beryllium copper, brass, bronze, iron, and steel.

The instrument is usually held by a loop of some form of thread or wire at the top curve, to enable the triangle to vibrate and it is struck with a metal rod called a "beater".

Iconography is the primary source for knowledge of the history of the triangle, and provides insight into the musical and social context in which the instrument developed.

[4][6] For decades, it was thought that the first iconographic witness of a triangle came from a 9th-century manuscript held at Emmeram of Regensburg, through longstanding writings by James Blades and others, although recent scholarship does not share this view.

[4] The first known use of the written term “triangle” occurs in an inventory list of the musical instruments owned by the kapelle in Wurttemberg, Germany.

[4] The list was compiled by Balduin Hoyoul in 1589, over two hundred years after the iconographic emergence of the triangle in the fourteenth century.

[4] In the early nineteenth century, Romantic-era composers began to seek new colors, and explored the sustaining qualities of the triangle.

[10] The triangle is often the subject of jokes and one-liners, as an archetypal instrument that seemingly has no musical function and requires no skill to play (the Martin Short character Ed Grimley is an example).

For complex, rapid rhythms, the instrument may be suspended from a stand using two clips, and played with two beaters, although this makes it more difficult to control.

[4] Wolfgang Amadeus Mozart, Joseph Haydn and Ludwig van Beethoven all used it, though sparingly, usually in imitation of Janissary bands.

[4][13] The earliest writing for the triangle is found in Cristoph Willibald Gluck's operas Der betrogene Kadi (1761)[14] and La Cythère Assiégée (1775)[4][15].

Albert Lortzing used triangles in the opening of his opera Der Waffenschmied to mimic the sound of hammers in a blacksmith's shop.