Mike, many thanks for replying.
I have only just managed to solve the issue and will describe the solution for the benefit of future readers.
Within my DAW (Reaper) one must proceed to add as many tracks as one wishes. Each track requires one to set the input. The default input was set to Mono, therefore preventing the full extent of the stereo signal produced by my digital piano to be recorded.
It was solved by asigning the first track to the vocal Microphone (Shure SM58), and adding a second track whith it’s imput set to “Stereo.” This second input was fed the signal from the digital piano. The digital piano was plugged into channels M3 and M4 via 1/4 inch plugs.
As you can see the issue was due to lack of skills using the Reaper DAW. Pretty basic, but I don’t doubt there are many out there with similar issues.
Again, many thanks for your reply.
Cheers!
Stephen