Another common chord used in Rock music is the seventh chord (sometimes called dominant seventh chord.) Seventh chords consist of four notes taken from the major scale of the same letter name. These notes are the 1 (first), 3 (third), 5 (fifth) and b7 (flattened seventh) notes of the major scale, so the chord formula for the seventh chord is:
A flattened seventh (b7) is created by lowering the seventh note of the scale by one semitone. Notice that the seventh chord is simply a major chord with a flattened seventh note added.
The G7 chord is constructed from the G major scale. Using the previous chord formula on the G major scale as follows, it can be seen that the G7 chord contains the notes G, B, D and F. When the seventh note of the G major scale (F#) is flattened, it becomes an F note.
Play the four notes of the G7 chord with the first, second, fourth and fifth fingers of your right hand, individually, and then together, as shown here.