Hi Tano,
Thank you. When I captured the original screen shot, the top box worked if the track had a Realtrack on it. To be honest, I think to try if the track had a midi file on it. Also, I clicked on the relevant track (in the above image "Bass"). I just noticed that if the "Default Synth" selection is active, that also requires the second box down.
Once again, thank you for the information.
Noel