It depends upon the type of instrument you play. Not all of them produce sound in the same way. For example, if you are playing the violin, it is played by drawing a bow on its strings. The other ways of playing include plucking the strings with the fingers or striking the strings using the wooden side of the bow. When vibration takes place in strings, they transmit to the top and bottom plate through the bridge. The same reverberates in the hollow body and hence, produces a rich sound. However, different instruments have different mechanisms to produce sound.