You can change the sound by putting at position 1-1-1 a program change controller. Just change it to the number of the drumkit you want the var to have. Now, you can put another program change at 1-1-1 for the other varations, but also in the one you change, you can put a program change at the last measure (eg measure 4) at position 4-4-127.

Hope this clears it up for you.

greetings!

Joost