         }
         // Start the engine.
         do {
-            self.engine.prepare()
+            engine.prepare()
 
             #if os(iOS)
 

        tester = AKTester(node, samples: samples)
        output = tester
        start()
        self.engine.pause()
        tester?.play()
        let renderer = AKOfflineRenderer(engine: self.engine)
        renderer?.render(Int32(samples))
    }


    /// Stop the audio engine
    open static func stop() {
        // Stop the engine.
        engine.stop()
        shouldBeRunning = false
        #if os(iOS)
        do {
