This project report details the development and results of an application created to modify musical pieces in the MIDI file format. Accomplishing this, the application modifies the music during real-time playback from user defined actions on the user interface. The user can change attributes such as tempo, volume, velocity, key, and the musical mode of loaded .mid files and perceive an immediate reaction from the playing musical piece. It includes four presets for users to quickly see a sample of the program’s capabilities. These presets correspond to video game states, which provides a theme for each preset, and are set combinations of the five previously mentioned attributes. These presets include combat, easygoing, cacophonous, and unsettling. This report contains a primer on certain basics of musical theory required to understand how the musical transformations are applied. In addition, further explanation of the activity flow, development process, and user tests are covered regarding the application. Finally, the fulfilled requirements and additional features of the software are summarized, and several features are forwarded as suggestions for future development.