A system and method for creating and/or rearranging musical content on a mobile device such as a cellphone or personal digital assistant (PDA), or on a computer for subsequent download and interactive playback on a mobile device. The method includes the creation and use of a digital music file, preferably consisting of MIDI sequence data, defining a musical composition having distinct musical parts, and the creation and use of a control file used in the rearrangement of the musical parts. The control file includes a plurality of control parameters for the musical composition, including which musical parts are active for each measure of the musical compositions. A user interface is included for allowing a user to alter one or more of the control parameters.