Related Chords
The most common related chords are those built on the fourth and fifth notes
of the scale.
![](images/2/index.90.gif)
For simplicity, these chords are often referred to just by their number—usually
with Roman numerals such as I, IV, and V. The V chord is G major in this case, and
the G7 is formed by adding the seventh note above the G.
![](images/2/index.91.gif)
Here, (a) shows the necessary components of the G chord: G, B, and D.
The seventh note above G is F, and adding this as in (b) makes a familiar G7.
The V chord is known as the dominant, and when the seventh is added it is known
as the dominant seventh.
The IV chord, F in this case, is also known as the subdominant. There are hundreds
of songs that only use the I, IV, and V chords, and understanding this makes it
easy to change key.
For instance, if you are in the key of C and the song feels too low for your
voice, you can try D a tone higher. The V chord in D, counting up the scale, is
A. A7 will be the dominant seventh. The fourth note of the D scale is G, so G will
be the IV chord or subdominant. So everywhere you had C as I chord, you may substitute
a D chord, and similarly you may replace the G7 chords with A7s, and the Fs with
Gs.
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