The disclosure relates to sound playback and editing apparatus. The editing apparatus uses user interaction to allow the user to instinctively modify recorded sound. This can be achieved by converting a quality of the user's physical interactions with the editing apparatus into instructions for processing the sound. For example, in one embodiment the user can mix sound files by ‘mixing’, i.e. shaking, physical representations of those sound files (such as the recording medium on which the files are stored) alone or together.