Spoiler: Download Lavender.mp3 and the sectrogram in your PC and listen to it with the sectrogram.
Within 2-3 minutes the Ghost appears in the sectrogram, if you listen to it much longer like 8-10 minutes the Ghost appears and spells ¨Leave now.¨ in Unown.
Don't know if this is true but when you get the message from the Ghost; depends on the version you encountered it, he will be in your house and will interact with certain colored objects.
Versions the Ghost is in: Red, Blue, Green (Jap.), FireRed, and LeafGreen. (I maybe wrong though.)