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 ...

A piece of 50,000-year-old string - the oldest yet discovered - found ... A study published in Scientific Reports said a tiny, three-ply cord fragment made from bark was spotted on a stone tool ...