Withdrawing from the recording contract, author rights?

I recorded the songs in Ibiza, Spain. I recorded the acoustic versions of my songs with two musicians. In the contract the percentage of mine author rights is higher then theirs, as they did only music arrangments. As my decisions about the songs, name of the songs, order of the songs, photo and cover of the album, were not accepting I want to withdraw from the contract. I would like to ask if and how it is possible. The album have not been released yet, but producer is going to do as soon as possible, as he know it is against my decision. Many thanks in advance for your response.