It seems that now it is possible to update your Nokia N73 to the music edition. The procedure is quite simple – change your N73’s product code to 0539343 and then use Nokia Software Updater to update your N73 to the Music Edition firmware.
The updated phone has the well-known Moby tune “In My Heart”, uses joystick controls to play music, and the media key on the phone becomes a one touch access to the music player.
But, be aware as this procedure will invalidate any warranty on your handset.
Source: AAS forums