What does Gatsby understand about Daisy's voice that Nick does not?
Gatsby's realization about Daisy occurs in Chapter 7 when he, Nick, and Jordan Baker are at the Buchanans'. During a moment when others are out of ear's reach, Gatsby tells Nick that Daisy's voice is full of money. Even though Nick understands Daisy and the fact that she may have married Tom for his money, this had never occurred to him before. He notes:
That was it. I’d never understood before. It was full of money—that was the inexhaustible charm that rose and fell in it, the jingle of it, the cymbals’ song of it . . . High in a white palace the king’s daughter, the golden girl . . .
Daisy is the "golden girl." She represents the American Dream to Gatsby. She is perfection to him. She is up on a pedestal, where the upper classes live. This is a social world that is full of money.
Remember that Gatsby has had to resort to corrupt means to achieve his own wealth. He goes after this wealth in order to reach Daisy's social circle, to put himself on her level. So, bound up with this idea of Daisy as his goal of an American Dream is the necessity of having money. Fitzgerald uses symbolism and certain cues in the novel to show this relationship between Daisy and money. One of the most noticeable symbols is the green light at the end of Daisy's dock. Gatsby basically worships the green light while he waits for his reunion with her. The color green becomes associated with Daisy and it is clearly associated with money. Therefore, the association of Daisy and money suggests she is part of a seemingly unreachable upper class and this has become part of her persona.