I don't understand exactly what you mean, but if you mean that cakewalk is not playing back the correct instruments, I suspect you did not load an instrument patch for the psr740!
You need to import the instrument definition for a PSR 740 if it's not in the instrument list!
Also make sure to turn echo off on all channels, while recording!
I don't own a psr 740 , so I have no idea what the settings should be on the psr740, but I do use a G 800 without any problem with CPA, in fact I use avarage four different instrument definitions in recordings and send
them out all at the same time, once ready for the audio recording, which does not need any
special settings on the different midi devices, due to the use of a midi-patchbay.
1. load the instrument definition
2. choose the desired project options
3. choose the midi channels you like to reserve for your psr740
Keyboards/Sound Units: Kurzweil 2600S, Roland VR-760, Acces Virus C, Roland G-800, Akai AX60, Minimoog, Machine Drum, Roland R8-M, mediastation x-76