There is a provided a method and apparatus for enabling a user to amend an audio file, via a user interface for controlling a driver for re-authoring the audio file. The method comprises the following steps: a) associating an icon on said user interface with one or more instruments or sets of instruments in said audio file; b) providing a selection of possible trajectories for each said icon, each trajectory defining the virtual path, relative to said user, of the associated instrument or set of instruments; c) providing a display on said user interface for showing the position of each said icon, each position defining the virtual position, relative to said user, of the associated instrument or set of instruments; d) the user selecting an icon; e) the user assigning a position and/or a trajectory from the selection, to the selected icon; and g) indicating, on said display, the position of the selected icon and whether a trajectory has been assigned to the selected icon. The invention relates in particular to a method for enabling a user to amend a MIDI file, via a user interface for controlling a driver for applying three-dimensional audio data to the MIDI file.