A method for playing a song employing a musical controller is disclosed. Program instructions are executed, and one or more music composition algorithms are applied to song data in accordance with a song data structure to generate music output for the song. User input is received for one or more musical components, and musical data in accordance with the song data structure corresponding to the musical components are generated or modified in accordance with the user input. The user input is provided via a controller, and the controller provides musical information via descriptors. The descriptors contain data that represent musical information, and the descriptors include data that does not represent sampled audio information. Music rules are applied to the modified musical data, and the music output for the song is modified in accordance with the modified musical data. As a first step the user is provided with musical data in accordance with the song data structure for a complete song, and in response to the user input a modified song is created based on user modifications to the complete song. The controller may be internal or external to a computing system, and may be a touchpad. The user input may modify music output corresponding to one or a plurality of instruments, audio samples or microphone input. The modified song may be stored for subsequent playback and/or played in real time as a live performance. The controller may consist of a guitar controller, a wind controller, a keyboard controller, a sequencer tool or a MIDI controller.