The Great Gatsby, singing compulsion

Could you please tell me what is a "singing compulsion" in the following excerpt from The Great Gatsby by F. Scott Fitzgerald, chapter 1:

I looked back at my cousin who began to ask me questions in her low, thrilling voice. It was the kind of voice that the ear follows up and down as if each speech is an arrangement of notes that will never be played again. Her face was sad and lovely with bright things in it, bright eyes and a bright passionate mouth—but there was an excitement in her voice that men who had cared for her found difficult to forget : a singing compulsion, a whispered “Listen,” a promise that she had done gay, exciting things just a while since and that there were gay, exciting things hovering in the next hour.

I precise that the narrators says also:

I've heard it said that Daisy's murmur was only to make people lean toward her.

Her voice compelled me forward breathlessly as I listened.

Thank you.