iOS switch between playing sounds in background and not playing

Question

I am working on music app and it has feature of switching between playing/not playing music when app minimized. How can I do it?

I use that code to enable playing in backgound, but how can I disable it?

    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
        try AVAudioSession.sharedInstance().setActive(true)
    } catch let error as NSError {
        print(error.localizedDescription)
    }