works when gameScene is loaded first , but play for half a sec and immediately stops (no error) when loaded by another scene, why ?

in the gameScene.swift:
declaration:

var backgroundMusic: SKAudioNode!

in didMoveToView:

  if let musicURL = NSBundle.mainBundle().URLForResource("Jalandhar", withExtension: "mp3") {
            backgroundMusic = SKAudioNode(URL: musicURL)
             addChild(backgroundMusic)
        }

i ended up using AVAudioPlayer to workaround it , code may be useful:
declare as property :

var audioPlayer: AVAudioPlayer!

then in a function :

 let filePath = NSBundle.mainBundle().pathForResource("musicfile", ofType: "mp3")
        let url = NSURL.fileURLWithPath(filePath!)
        do {
            audioPlayer = try AVAudioPlayer(contentsOfURL: url, fileTypeHint: nil)
            audioPlayer.play()        }
        catch {
            print("music error")
        }