Yeah good reply dirt. One thing though, when you refer to a b6. By Music Theory terms, that description is incorrect and there is a good explaination. It's is always augmented (#5), rather than a b6. b6 makes it is sound like it's on the minor side of the harmonic spectrum. Even in a minor 6 chord the 6 is natural. The b6 as you said only occurs in augmented chords, as #5. This also helps alot in the use of this note harmonically. If the chord your harmonizing over ommited the 5th, this note will work. Sort of as a tweaked harmony (thus augmented). Often performed by bending the 5th up a half step. It rarely done the other way around, like sliding back from the natural 6 to the b6.