Percussion instruments can be divided into two groups; those that make a distinct tone and those that do not. Pianos, xylophones, marimbas, steel drums and some tuned drums (for example tympani) are percussion instruments that have distinct tones. In other words, their overtones are harmonic. Cymbals, wood block, llaves and most drums, on the other hand do not produce a tone. This Wikipedia link has a long list of percussion instruments with links and explanations for each.