The only way I know how to do this is to push both up and down volume buttons simultaneously for the chord and accomp. and bass parts leaving only the drum, upper and lower parts with volume. You will notice the parts you turned off as having volumes of 0 on the screen. Now, you can split the keyboard using manual bass or making a program with splits and only the drums will play. Unfortunately, these still requires you to double click the volume buttons of sounds you want off. Once done though, even when you change to other styles, the drums will sound by themselves.
George Kaye
Kaye's Music Scene