iTunes, multiple copy of a single song

I am using iTunes as my music library. However I have copies of the same song on multiple drives. Is there a way I can add all the file locations, so that when one drive is not available, it will automatically play the song from the other drive?

Are all copies of the songs on removable or external storage?
Lets say you have song 1 on the internal and external drive, only put Song 1 that is on the internal drive into Itunes.

Zepher said:

Are all copies of the songs on removable or external storage?
Lets say you have song 1 on the internal and external drive, only put Song 1 that is on the internal drive into Itunes.

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I've one copy on an external drive, and another copy on a networked drive. I don't store a copy on my internal drive. The folder/file structure of both the networked drive and the external drive is exactly the same.