To change one's tune typically means to change in a more positive or agreeable way, which is what the sentence describes.
Context: "Ok, in your next book instead of making the gamble you make it so that Ray is portrayed in a more positive light as a cross between Clauswitz and Gandhi. " Claim: "Ok, in your next book the gamble you rather change your tune and ray is portrayed as a cross between clauswitz and gandhi."
Considering the context, is the claim true, false, or unknown?