These are solid instruments. They vibrate to produce a sound when struck, shaken, or scraped such as a bell, gong, or rattle. Idiophonic instruments or self-vibrators, i.e. instruments of solid substance which, owing to their elastic nature, have a sonority of their own, which is emitted in waves when they are struck, plucked, or stimulated by friction or air.
The instruments of this group are usually played with a striker or hammer. These instruments are not capable of producing definite pitches that are required for creating a melody. That is why their use is limited in classical music.