Wind chimes are a type of percussion instrument constructed from suspended tubes, rods, bells or other objects that are often made of metal or wood. The tubes or rods are suspended along with some type of weight or surface which the tubes or rods can strike when they or another wind-catching surface are blown by the natural movement of air outside. They are usually hung outside of a building or residence as a visual and aural garden ornament. Since the percussion instruments are struck according to the random effects of the wind blowing the chimes, wind chimes have been considered an example of chance-based music. The tubes or rods may sound either indistinct pitches, or fairly distinct pitches. Wind chimes that sound fairly distinct pitches can, through the chance movement of air, create simple melodies or broken chords.