I would suggest going back to OS 3.0c , unless the 4.0b OS that will be released ( or is relased) by Ketron fixes the latency problem . If OS 4.0b works , this would allow the end user to have what ever sounds they choose ,3.0 sounds or 4.0 sounds. When will 4.0B arrive ? I was told any day now . A list of changes for 4.Ob was sent to the soltonclub from Antonio (Italian Club) . Look for that email . Dan