Guitar skills: 'Add’ chords come in the form of either ‘add9’ or ‘add11’. The name tells you to add either a 9th or 11th interval to a basic major or minor chord. So, Cadd9 is a C chord ...

The 9th (D) is provided by the open first string. Play a regular C chord and you’ll get Cadd9. The 6th (D) appears on the open fourth and first strings here, giving this chord an unusual feel ...