Daisy's Voice is Full of Money.
" "She's got an indiscreet voice," I remarked, "It's full of -" I hesitated.
"Her voice is full of money," he said suddenly.
That it was." Fitzgerald, page 120
I believe the point Fitzgerald is trying to make with this little situation that occurs, Nick thinking about Daisy's voice, is established in order to further explain to the reader that Daisy's life is exceedingly care-free, so much in fact, that you can literally hear it in her voice. It is obvious that by the pending affair between Gatsby and Daisy, that Daisy does not care when Tom begins to realize what is going on. It also suggests that Daisy emits a sense that she has always been provided for, as well as educated, always around rich folk, so she speaks as they should. Nick is sort of comparing her voice to that of his own, or to people around him, like Gatsby, and probably notes that they are from a working class, and Nick seems to realize how hard he has to work at speaking with these folk, since he has never really been a part of the wealthy cliques. He hesitates frequently, thinking before he speaks around these people. Daisy, on the other hand, is free to do and say what she wishes, without worry, because she is so accustomed to living in this world.