Question

why were the nightingale shivering and her voice quivering

Answer 1

nightingale was shivering and her voice was quivering because the frog made her practice so much that she got weak and was not able to sing properly

Answer 2

Nightingale was shivering and Her voice was quivering due to a lot of practice of 6 hours in the bad weather which was not at all suitable for her