Dick Clarke Jazz Guitarist

Diagram 1 is a fairly familiar A7 chord.   The guide tones for this chord are shown on diag 2.  the G on the 4th string (red dot) is the seventh of the chord and the C sharp on the 3rd string is third of the chord.  The third and the seventh of a chord are what are normally thought of as the guide tones.  The third helps the ear identify the chord as major or minor, and the seventh also helps us to tell whether the chord is major, minor or dominant.

Diag 3 is a fairly familiar D7 chord.  This might very well be the next chord in a blues sequence in the key of A, it is the next chord from A in the cycle of fifths which is a common progression in all kinds of music.  The guide tones for this are C (the seventh) and F sharp (the third).  Notice that the guide tones have slipped down one fret from the A chord, and that the third (blue dot) and the seventh (red dot) have swapped strings, they have ‘inverted’. as shown by diag 4.

If you slide the D7 chord two frets higher up the neck you have an E7 chord as shown in diag 5.  These three chords are all you need to play a simple 12 bar blues in A.

The guide tones in the E7 (diag 6) are the seventh, D (red dot) and the third Gsharp (blue dot).  They have also inverted as compared to the A7 chord.