The Wise Daughter Riddle

Riddle: Many years ago, a wealthy old man was near death. He wished to leave his fortune to one of his three children. The old man wanted to know that his fortune would be in wise hands. He stipulated that his estate would be left to the child who would sing him half as many songs as days that he had left to live. The eldest son said he couldn't comply because he didn't know how many days his father had left to live, and besides he was too busy. The youngest son said the same thing. The man ended up leaving his money to his third child, a daughter. What did his daughter do?