Helen ST, I think I've figured out how to do that twisted cord!
Take one length of yellow and one length of black, lay them together, and tie them together at both ends. Now you have a circle. Put a big toe through the circle and pull the yarn up so you have a very narrow ellipse; pull the yarn around until the two knots are together. Spin the loop S-direction -- turn the top end clockwise. When you think you've twisted it enough, keep it taut while you use the other hand to take hold of the ends sticking out of the two knots and then use the first hand to free the loop from your toe, transferring it to your finger that has the other end. Let go of the knots. It will spin itself Z-direction! Not cleanly; there will be little loops around -- so take hold of the ends sticking out of the knots again and pull it straight, then let go again. Repeat until it behaves. Tie the ends, and twice in the middle -- cut between those two new middle knots, and the loops at the ends. And you have exactly what those pictures showed.
If it doesn't ply itself very tightly, take hold of the loops and pull it apart, put one back on your toe, and spin it more.
Cece