Help, please! :)

What kind of contract do I need to gain the rights to a master recording from the producers & songwriters? I know there are publishing contracts (only if a publisher is involved) and then producer contracts. But what do I need to cover the producer & songwriter and set the royalties split. Or will a producer agreement PLUS a songwriter agreement cover everything I need? So the songwriter agreement sets out the split and then the producer agreement will give us the rights to the master?

Thanks!