ITunes Help......"missing" music files?

I had a similar problem I couldn't find all my Elton John Music so I went to the My Music Folder and looked in all folders and sub-folders. I found the music and I opened Itunes and dragged the songs from the sub folders to to the library in Itunes. Look in Itunes folder and itunes music folder and the sub folders within them. If you just add music to your computer itunes doesn't automatically find it and add it to the library. when you play the song file from the My Music folder is when itunes will add it to the library or if you buy there songs of course it will.