Dominant 7th Chord

Introduction

Seventh chord is a combination of major triad chord with minor interval of 7^th.Actually,dominant 7 chord is major,the 7^th note come from minor scales.A major triad chord and minor 7^th interval are combined together to form ‘dominant seventh’ chord.It’s is write as 7 such as A7,B7,C7.It’s easy to create a dominant chord from scale,for example  to create C dominant 7 chord.Firstly,list all notes from C major and C minor.Look 

below

C major : C,D,E,F,G,A,B

C minor : C,D,Eb,F,G,Ab,Bb

Secondly,create chord C major C-E-G.Then,pick up 7^th  interval notes from minor C scale.The 7^th note is Bb.Then combine major chord with 7^th interval from minor scale to form new dominant 7 chord C-E-G-Bb.Same with other chord A7,B7,C7,D7,E7,F7,&G7.Use same method to create Dominant 7 chord.

Dominant 7 chord actually use as ‘blues chord’ that have 4 note,3 major triad and 1 seventh  minor interval.Diagram below show some dominant 7 chord were create from major scale

Root	Major scale	Minor scale	Major chord	Dominant 7 chord
A	A,B,C#,D,E,F#,G#	A,B,C,D,E,F,G	A-C#-E	A-C#-E-G
B	B,C#,D#,E,F#,G#,A#	B,C#,D,E,F#,G,A	B-D#-F#	B-D#-F#-A
C	C,D,E,F,G,A,B	C,D,Eb,F,G,Ab,Bb	C-E-G	C-E-G-Bb
D	D,E,F#,G,A,B,C#	D,E,F,G,A,Bb,C	D-F#-A	D-F#-A-C
E	E,F#,G#,A,B,C#,D#	E,F#,G,A,B,C,D	E-G#-B	E-G#-B-D
F	F,G,A,Bb,C,D,E,	F,G,Ab,Bb,C,Db,Eb	F-A-C	F-A-C-Eb
G	G,A,B,C,D,E,F#	G,A,Bb,C,D,Eb,F	G-B-D	G-B-G-F

Get Dominant 7 Chord pattern here