#2
You use intervals when building chords, scales, and explanaining relationships between notes if that helps.
#4
Diminished 7th is used in construction of a diminished chord: 1 b3 b5 bb7.

Augmented 2nd and augmented 5th are used with a lot of 7th chords to add tension. The "Hendrix Chord" has an augmented 2nd.

As for an augmented 6th, it probably has a use, but I haven't gotten around to it.
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#5
The augmented 6th is almost everytime referred to as b7.
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#7
Sharp second doesn't make any sense when you say it like that. It's usually referred to as a #9.

The intervals are:

m2
M2
m3
M3
P4
Tritone
P5
m6
M6
m7
M7

If you mean a major second plus one half step, that makes it a minor third. Those are used to construct minor chords.

An augmented fifth is enharmonic to a minor sixth. They are what determines an augmented chord (Root, 3, #5)

Sharp sixth is pretty much unheard of. It's typically called a minor seven, which has already been said. They are used to make the dominant seventh chords.

A diminished seventh is enharmonic to a major sixth. This was used more heavily during the common practice period of music from 1600-1900, but not as much today.
Last edited by GuitarGod610 at Sep 19, 2006,