Agreed. And the rest is gravy. As long as the terms of the Kickstarter are filled (rewards, i.e. digital download of the music) there is no further responsibility. In fact, Kickstarter does not even have protections if the person who runs the Kickstarter flees with the money and delivers nothing. It's all very carefully laid out to provide no risk to Kickstarter or the people who list. There are many cases of people running away with large sums of money or trying earnestly and failing to deliver what they said they would.
I am not saying any of this will happen here.
I am saying that backers are in no position to demand extras beyond the reward pledged, mentioned above.
There is plenty of time for people to pull their money out if they're not satisfied with that arrangement. Everything will go along without you. It doesn't seem like a terribly complicated business arrangement from the "backer" perspective on this one.