Sound in 2 different apps


I am running Audible and would like to be able to run a game at the same time without listening to the game. I have setup the 2 to have different sound levels individually; but When i run audible then switch over to the game the game music plays simultaneous with audible; I would like to designate audible as the only active sound. The game app does not have discrete sound controls. I have already discussed this with the programmers of the game and they have no plans to change that. Is there a setting or an app that would allow sound to play in one application while muting another?