{@link gui.DGuitar DGuitar}, has a DestktopPane that contains JInternalFrames that can be PieceInternalFrames or MidiInternalFrames.
PieceInternalFrames contain a single PiecePanel that contains many TrackPanel.
TrackPanel may cotain one or more BarPanel that contain different Bars.
MidiInternalFrames are used to display and play the MIDI files.