I created an app and I am attempting to allow the user to continue to listen to their music while playing my game, but whenever they hit \"play\" and the ingame sounds occur
You need to set the AVAudioSession category, with one of the following value: https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVAudioSession_ClassReference/index.html (AVAudioSession Class Reference).
The default value is set to AVAudioSessionCategorySoloAmbient. As you can read :
[...] using this category implies that your app’s audio is nonmixable—activating your session will interrupt any other audio sessions which are also nonmixable. To allow mixing, use the
AVAudioSessionCategoryAmbientcategory instead.
You have to change the category, before you play your sound. To do so :
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryAmbient, error: nil)
AVAudioSession.sharedInstance().setActive(true, error: nil)
You don't need to call those line each time you play the sound. You might want to do it only once.