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Do you know the difference between dominant 7th and major 7th chords?

By Mike Hayes | May 17, 2010

If there is one area of basic harmony that tangles and snares
newbie players it’s the seventh chords. Dominant seventh chords
are often confused with major seventh chords; the dominant
seventh variety are structurally different from the major seventh
and perform an entirely different musical function.

Here’s a quick review, even if you already know this stuff you
might want to take another look just to be sure you have your
ears pinned on straight.

Basic harmony review:

Chord construction

Major seventh construction: 1 – 3 – 5 – 7

Dominant seventh construction: 1 – 3 – 5 – b7

Chord symbols

The significant thing to remember is that major seventh chords
are indicated as (Maj7) e.g., CMaj7 whereas the dominant seventh
chord is simply indicated as (7) e.g., C7

So there you have it! Whenever you see a C7 it is a dominant
seventh chord not a major seventh … remember that, most
guitarists do not know (or play as if they do not know) that
basic piece of essential information.

Chord function

The major seventh chord can be substituted for a major chord;
whereas the dominant seventh is always the fifth chord of a
diatonic scale.

Some examples shown in the key of C to help clarify things.

In any basic triadic (three note) harmonization of a major scale
chords 1,4 & 5 are major triads e.g.,

triadic version

1 = C
2 = Dm
3 = Em
4 = F
5 = G
6 = A
7 = Bdim

Notice how chords 1,4 and 5 are major triads, if we where to move
on to the scaletone seventh (four note) version of the same scale
we would create the following chords.

scaletone seventh version

1 = CMaj7
2 = Dm7
3 = Em7
4 = FMaj7
5 = G7
6 = Am7
7 = Bm7b5

Notice how chords 1 and 4 change from major triads to major 7th
chords, whereas chord 5 (previously a major chord) converts to a
dominant 7th chord.

As you can see a G7 chord belongs to the key of C because it was
created from that key, a G7 is not created from the key of G.

This is very important information for the lead guitarist to know
so that when they encounter a dominant seventh chord they will be
able to identify it’s parent key, Here is a list of dominant
seventh chords and their parent keys, learn this table it will
save a lot of trial and error practice.

G7 => C
D7 => G
A7 => D
E7 => A
B7 => E
F#7=> B
C#7=> F#
Ab7=> Db
Eb7=> Ab
Bb7=> Eb
F7 => Bb
C7 => F

In the following chord progression (Ex 1.)the lead guitarist
could safely play notes from the key of C as all chords are
derived from that key.

Ex 1.

C ///| CMaj7 /// | FMaj7 /// | CMaj7 /// ||

However in this progression (Ex 2.) the key centre of the song
changed to the key of F in bar two (C7)

Ex 2.

C ///| C7 /// | F /// | etc…

Important: Even though the key signature of the song may remain
the same on the sheet music the experienced player knows how to
de-code the chord symbols to reveal the true harmonic movement
throughout the piece.

Study this information, play both the major seventh and dominant
seventh chords s-l-o-w-l-y and paying close attention to the
differences in chordal texture, if you take the time you will
hear that the dominant seventh chord has a ‘roaming’ or
‘restless’ nature whereas the major seventh has a ‘peaceful’ or
‘contented’ feeling.

Remember your ear will only take you so far, that’s when your
theory kicks in and helps you find the sounds you are looking for
on guitar.

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