We developed a kinetic particles synthesizer for mobile devices having a multi-touch screen such as a tablet PC and a smart phone. This synthesizer generates music based on the kinetics of particles under a two-dimensional physics engine. The particles move in the screen to synthesize sounds according to their own physical properties, which are shape, size, mass, linear and angular velocity, friction, restitution, etc. If a particle collides with others, a percussive sound is generated. A player can play music by the simple operation of touching or dragging on the screen of the device. Using a three-axis acceleration sensor, a player can perform music by shuffling or tilting the device. Each particle sounds just a simple tone. However, a large amount of various particles play attractive music by aggregating their sounds. This concept has been inspired by natural sounds made from an assembly of simple components, for example, rustling leaves or falling rain. For a novice who has no experience of playing a musical instrument, it is easy to learn how to play instantly and enjoy performing music with intuitive operation. Our system is used for musical instruments for interactive music entertainment.