um, yeah but don't worry, you're making me a bit confused also. What voltage divider are you referring to? There shouldn't be any extra reference voltage required as you have the ground reference.
Split rail means that you have a positive, a negative and a ground rail. The opamp should be referenced to the ground rail and supplied power from the positive and negative rails. The input and output must also be referenced the same ground rail (i.e. connect the plug shield to the ground rail), or you will get a DC offset (which wastes power).