What do you make of the reference to 'the tuning-fork that had been struck upon a star' in The Great Gatsby?
I take it that Gatsby is waiting for a moment before kissing Daisy, so as to almost mark the end of that chapter of his life and the beginning of another, where Daisy is everything to him. But what significance does Fitzgerald's choice of metaphorical background sound make here?
Gatsby is rather thoroughly associated with dreaming, the power of dreams, and with a sense of (great) destiny. The metaphor here ("tuning fork struck upon a star") is in keeping with this characterization of Gatsby.
Early in the novel, Nick describes Gatsby as having "an extraordinary gift for hope":
"...there was something gorgeous about him, some heightened sensitivity to the promises of life.… [Gatsby had] an extraordinary gift for hope, a romantic readiness such as I have never found in any other person and which it is not likely I shall ever find again."
Later, Nick describes Gatsby as believing “a promise that the rock of the world was founded securely on a fairy's wing.” These depictions of Gatsby are perfectly in line with the idea that Gatsby's sense of reality is in tune, metaphorically, with a celestial destiny, a great promise, or a sense of being engaged in a waking dream.
The pitch of reality, for Gatsby, is set to his own vision. He only accepts as real that which fulfills his sense of his own destiny. This can be seen in his refusal to accept any reason why he can't "repeat the past" or why he may not be able to claim Daisy, ultimately, as his own. Gatsby does not see her marriage to Tom as a serious obstacle. He also does not see his profession (as a bootlegger, white collar criminal, etc.) as a problem.
Rather, Gatsby insists on seeing what he wants to see - the possibility of achieving his ideal vision. With his "gift for hope" and "sensitivity to the promises of life", Gatsby is metaphorically in tune with the reality of his ideals (not the reality of everyday life, of obstacles, troubles, or what we might call common reality).