Cut a piece of rope approximately 2 1/2 feet long. The length of the rope may be different depending on your preference for how close you want the cello to be to you.
Tie one end of the rope into a small loop. Ensure the loop is large enough that it will fit around the cello endpin. Tie the other end of the rope so that it is large enough to fit around the leg of the chair.
Connect the larger loop to the leg of the chair by lifting the chair and putting the chair leg through the loop. Straighten the rope and place the cello endpin through the loop at the end of the rope.