This paper presents a highly functional audio player, called Drumix, that allows a listener to control the volume, timbre, and rhythmic patterns (drum patterns)of bass and snare drums within existing audio recordings in real time. A demand for active music listening has recently emerged. If the drum parts of popular songs could be manipulated, listeners could have new musical experiences by freely changing their impressions of the pieces (e.g., making the drum performance more energetic)instead of passively listening to them. To achieve this, Drumix provides three functions for rearranging drum parts, i.e., a volume control function that enables users to cut or boost the volume of each drum with a drum-specific volume slider, a timbre change function that allows them to replace the original timbre of each drum with another selected from a drop-down list, and a drum-pattern editing function that enables them to edit repetitive patterns of drum onsets on a graphical representation of their scores. Special musical skills are not required to use these functions. Subjective experiments revealed that Drumix could add a new dimension to the way listeners experience music.