@Override
    public void cloneFields(Cloner cloner, Object original) {
        // Duplicating the old cloned state from cloneForSpatial()
        this.initialized = false;
        this.started = false;
        this.played = false;
        this.audio = cloner.clone(audio);
    }
This method clone the Track and search for the cloned counterpart of the
original audio node in the given cloned spatial. The spatial is assumed
to be the Spatial holding the AnimControl controlling the animation using
this Track.

@param spatial the Spatial holding the AnimControl
@return the cloned Track with proper reference
jme3-core/src/main/java/com/jme3/animation/AudioTrack.java