Lots of songs use only the basic chords (major and minor),but there are also
many songs that use 7th chords. 7th chords are made up of 4 different notes
unlike regular major and minor chords that contain only 3 different notes.
That’s why they sound a little bit more interesting and complex. You will hear
these chords used frequently in jazz, r&b and blues but they may show up
occasionally in some rock songs.
The 3 main types of 7th chords are – Dominant7, Major7 and Minor7. When you play
a G dominant 7 chord, it will be written as G7 (the word “Dominant” is omitted).
When you play a G major 7 chord, it will be written as G major 7 (the word major must
be included). When you play a G minor 7 chord, it will be written as G minor 7
(all minor chords must include the word “minor”).
Below are 3 common forms of Major 7, Minor 7 and Dominant 7 chord forms.
All of these forms can be put into any key by lining up the root (the lowest note in the chord)
to the note you want. To make this easy I’ve included a chart of the guitar neck.