Yamaha CP40 midi to S970 transpose errors

by Pete
(Barnstaple, Devon, UK)

Hi.

I have a Stage CP40 now midi'd to a PSR S970 and, being uneducated in this area of tech, have almost managed to accomplish what I want except for a transpose problem.
When I play the CP40 (my control keyboard) and transpose, say, up a semitone, as long as I continue playing the CP40 everything is fine with the S970 accompaniment, etc. But if I then play the S970 as well I find it has transposed out of tune.
Any help with this would be much appreciated.