When I set up a soft synth (any of them) I hear both the general midi sound and the soft synth sound when recording or playing. After I record, when I play back I only hear the soft synth.

How do I turn off the midi sound altogether under all circumstances when using a soft synth. Tried playing with echo buttons but nothing seems to work.

The keyboard synth has audio output (in addition to the midi output). I'm guessing that the keyboard audio outs are connected to some input so that you can hear the keyboard. I make the keyboard sound go away by turning down the volume control on the keyboard. --Larry

Do you have a keyboard connected via usb as a controller? If so do you have the audio from the keyboard also connected?  if so then do what larry suggested. 

Do you have multiple soft synths running? if so, then you need to assign midi channels to be unique to controller.