In our previous study, water was continuously spouted to the water surface. When music is played by a common aerodynamic music instrument, the time of the note is generally shorter. Therefore, the basic experiment on the present water music instrument has been carried out under the same short time condition with the music aerodynamic one. The main purpose of the present study is analyzing the generating mechanism on rain-drop music instrument. As the results, at time of about 50msec after the water jet hits against the water surface, the sound is generated. The presence of the resonance tube makes a longer resonance time. When a part of the resonance tube is sunk below the water surface, the dominant broadband components of a sound pressure spectrum shift to lower frequency side.