The following is 1 part of 7 lessons. The key of G is the first. It has more detailed explanations. You may want to visit The Key of G if your are unfamiliar some of the terminology.

ex.1 scales

D major scale

G major scale

A major scale

Chord enrichment of the I (D), IV (G),  V (A7) chord progression in the key of D.

ex.2major chords

D

G

A7

ex.3 add 9

Dadd9

Gadd9

A9

ex.4 suspended

Dsus

Gsus

A7sus

ex.5 6 chords

D6

D6 (option 2)

G6

A13

ex.6 maj7

DMaj7

GMaj7

A13