You know it from…

The Police–Every Breath You Take Opeth – Windowpane Pearl Jam–Elderly Woman Behind The Counter In A Small Town

How it works…

‘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 with an added 9th interval. Look at two octaves of the C major scale (CD E F G A B C D E F G A B) and you’ll see that the 9th and 11th notes are D and F.

When to use it…

Use major add9 and add11 chords for a rich, bright sound with a more sophisticated vibe than the more basic major chords.

For a dark, dissonant but sweet sound

Bands like Opeth make use of the minor add9 in particular, because the minor 3rd gives a dissonant yet somehow still sweet clash with the 9th.