Many people wonder why sanctus, or holy, is recited three times. It has nothing to do with the music, it is a language thing.
For an english speaking person to say "the holiest" they just say "the holiest." However, the Hebrew language does not allow for words like holier or holiest. Instead, to create a comparison word like holier, they just repeat the root word. Therefore holier is really holy holy. The word holiest is holy holy holy.