@Override
    public void setVolume(float f) {
        if (node != null) {
            node.setVolume(f);
        }
        volume = f;
    }
For streaming music only. (May need to loop.)

@param ar for rendering audio (not null)
@param am the AssetManager for loading assets (not null)
@param fileName the path to the audio asset (not null)
jme3-niftygui/src/main/java/com/jme3/niftygui/SoundHandleJme.java