altered fifth; +5 -5

WE've looked at augmented chords as trids.

Chords bigger than triads can have the 5th of the chord augmented or sharped.

The most common case of this would be an alteration of a dom 7th chord:
7 aug5
aug7
u(_5)
U#5
+7
7+

This chord usually functions as a regular dominant 7th chord but the augmented 5th gives it added flavor.
Listen to the difference in sound in the following passage.

C7+5

Such an alteration of 5th requires a melody that fits the chord.
Melody cannot have a 5 in there.

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a maj7 can also have 5th augmented.
It is not common but seen in contemporary jazz charts.

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-5 chords

Just as a dom7th chord can have its 5th augmented, so can it have its 5th diminished (flatted).

This is a more colorful variation of a plain dom 7th.
It is generally used for similar functions.

This is a good chord to know as it is very common in jazz and contemporary Lain tunes such as Bossa Nova

it is frequently used by jazz players as substitute for a plain dim 7th, melody line permitting.

Em7 A7 Dmaj7

Em7 A7b5 Dmaj7

they sound different.


C7b5

1 3 b5 b7