Originally Posted by: magicninjaWhat I don't get is why Gb isn't called a minor 5th and why you refered to it as a diminished 5th. :confused: I'm sorry if it's something easy I'm overlooking. :o

Well, that's because the 5th is what's called a perfect interval. Example: in Amin, the 5th is E. In Amaj, the 5th is E. There are no major or minor fifths, so reducing the fifth a half step makes it diminished, and raising it a half step makes it augmented.