this is reaLLY GOOD aagr caps :P. gain is sound volume. find the machine you want to change the gain on, you will find it as gain, volume, master vollume... etc and make a track on the timeline. double click to make a sound thingy then edit away!
I personally love the drums lol everything else is good and blends together OK. The transition at 1:10 was pretty good, good work!