Documentation Only (no JS Definition)
The JSON format used for add-in fingerings. Frequently you'll add this to indicate "nutting" or "barring" with one or more fingers.
For example, the D7 is often played by laying the index finger across the entire second fret and then placing middle finger on 3rd fret of "A" string like this: >pre< G C E A
- - - - (1st fret) X X X X - - - X - - - - (4th fret) </pre>
The "A" string has two fingers on it, obviously one does nothing -- except to make the chord much easier to play.