triangle, in music, percussion instrument consisting of a steel rod bent into a triangle, open at one angle, and struck with a steel rod. Only since the end of the 18th cent. has it been an orchestral instrument, although it appeared in Europe much earlier. Its tinkling sound is of indefinite pitch and therefore blends with whatever harmonies the orchestra produces.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.