Just a note: I have never tried Rock Band drums so I don't know the connection area.
Step 1: What You Need
1 Audio splitter from Radio Shack. You should find this pretty easy for $2. This is the main thing you need. This is what makes 2 people with their own headphones listen from the same audio output.
Step 2: How It Works
Since the foot pedal has 1 and we are using a headphone splitter, the second ring is empty.
Step 3: Placement
2. Plug in the audio splitter to the foot pedal connector on the drum.
3. Verify that all connections are secure and no tangled wires for optimal performance
Step 4: You Are Ready!
1. Go ahead and start up the game
2. Play a song where the drum starts out last or later on...
3. See if both foot pedals respond.
Now you can nail those songs with a double bass! Overkill by Motorhead is no sweat or leg pain
Note: I have mod my drum even further inside so I now have2 yellow and orange cymbals. If I get the time, I will make an instructable for it but it won't have many picture because it is finished. I need to build a stand like thing that will be like a hi-hat.