Finally I can push some of the changes I’ve made to cocos to add the ability to play each effect with a different volume parameter.I’m slowly pushing the changes to that fork: https://bitbucket.org/nesdavid/cocos2dx/ from the 2.1.4 release and all the changes are going to be in the branch sound
More specifically this is the latest commit: https://bitbucket.org/nesdavid/cocos2dx/commits/b884d45b4354467d4111aa1f74bfc43e10fff0b8
Expect the android (java code) in the following days and the ios version later next week.
This feature already implemented in 3.x (see gain parameter in SimpleAudioEngine::playEffect).
I’ll keep uploading it anyway until 2.1.4 is fully deprecated.