just follow the steps above, press menu, sound, mixer, other parts, other parts and on the left or right select function, change sound, pan, volume etc, and at the bottom select the root bass channel.

Mike can tell you exactly what sound he meant on the 7k since there are many more organ samples, as long as you play the right octave, which can be adjusted with key shift +/-12 on page 5 of the mixer, many sounds on your 60/ew65 will do. There is an organ bass in electric organ, or use cathedral or full organ or 16' & 1' ? You could put a sound edit into root bass for example.