It took over two hours, but I finally got my Rock Band drum set to play real drums via Reason on my PC. I had to visit a bunch of different web sites and tried out at least six different programs to get it to work, so here are the instructions - all in one place - if you're looking to do the same thing.
Step 1: Plug in the drum set to your computer via USB if you have the Xbox 360 version like me. Windows might automatically recognize it, or you might have to let Windows search for the proper driver (by following the prompts that appear after you plug it in). It took a few minutes but it finally worked.
1A (optional): Go to Control Panel/Game Controllers (Control Panel/Printers and Other Hardware/Game Controllers in XP) and click on Properties. There you can try hitting the drum pads and see if they register in the calibration program (I will have pictures of everything up soon).
2: Download and install Bome's Mouse Keyboard. This is a virtual Midi controller which will allow you to control Reason via your keyboard. Their website is great, and a lot of what I'm going to post next comes directly from there or from links on their site.
3. Download and unzip JoyToKey. This program will allow you to set specific keyboard keys to your game controller (ie the Rock Band Drums). So you will eventually set the kick pedal on the drums to the 'Z' key on the keyboard using this program (and the 'Z', in turn, will be set to control something in Reason via Bome's Mouse Keyboard).
4. Download and install Maple Virtual Midi Cable. This is simply a virtual Midi Input/Output driver that you will need to 'connect' Bome's Mouse Keyboard to Reason. You will need to restart your computer after installing this.
This next section is taken - almost verbatim - from here. You'll want to follow along on that page for now since it has helpful pictures.
5. After the restart, launch Bome's Mouse Keyboard. Go to File-Import-Knob Presets. It will open a folder where you will select the Presets folder, and then select the 'Reason3_Knobs.ini' preset (they've already created one specifically for Reason. Pretty damn cool). Select 'Add to Existing Knob Presets'. You should get a notice saying the knob loaded successfully.
5A. Go to Knobs-Presets and select the Reason preset you just loaded. Now you should see 10 knobs in the upper right corner of Bome's Mouse Keyboard.
5B. Go to Midi Out and select the first Maple MIDI item you see. This is the virtual Midi cable you installed earlier.
6. Launch Reason. Go to Edit-Preferences. Select the Audio page. Make sure 'Play in Background' is selected.
6A. Switch to the 'Control Surfaces and Keyboards' page within Preferences. You should be able to select 'Bome' as a manufacturer, and then 'Mouse Keyboard V2' as a model. Finally - very important - select the same Maple MIDI item as the 'MIDI Input' as you selected for the 'MIDI Output' in Bome's Mouse Keyboard.
Then click OK.
6B. You should have the option to Make Master Keyboard (if it isn't already). Click that button to make Bome your Master Keyboard for Reason.
6C. Now set up a ReDrum box in Reason, select a drum patch, and then make sure Bome's Mouse Keyboard is active (that means click on it). Hit the 'Z' button on the keyboard - you should see one of the little keys on the Mouse Keyboard depress, but there probably won't be any sound - I had to set the Mouse Keyboard to play an octave lower (I think it was in Options, but I will double check this). After setting it an octave lower, press the 'Z' key again - a different key on the Mouse Keyboard will depress (the very first key on the left) and you should hear a drum!
7. Now launch JoyToKey. Also bring up the Game Controllers-Preferences screen (from step 1A). Determine which button each drum pad controls, for instance, I think the kick pedal is Button 6. So double click on Button 6 in JoyToKey, which will open up another window, and then hit 'Z' to set the kick pedal to the 'Z' button on your keyboard ('Z' always controls the kick drum in Reason's ReDrum kits). Then set the red drum to the 'S' key if you're right-handed (the snare drum). The other three drum pads are up to you, since different Reason drum kits have different sounds set to different places. You can play around with your keyboard first - try all the keys from 'Z' to 'B' and 'S' to 'G' to see what does what, and then set your drum pads to the desired keys via JoyToKey.
8. Latency. It only took me a little over an hour to get to this point, but I had a big latency issue, where I would strike the drum and a split second later the drum sound occurred. It was very close, but once I started trying to play a beat that slight difference made playing impossible.
It took forever, but I finally figured out how to fix it. Just go to Edit-Preferences in Reason and go to the Audio page. Try to select the specific ASIO driver for your soundcard in 'Audio Card Driver' (if it has one). I then tried playing with the 'Latency Compensation', but this didn't really do anything. I finally had success by clicking the 'Control Panel' button (still on the Audio page) and selecting a very low latency there.
I guess other people have had success by altering the latency or the buffer size directly in their soundcard's software.
And that's it. When I finally got it working I seriously felt like it was the greatest accomplishment of my life. It's the coolest thing ever. Hope this helped, and again - I will post pictures soon to help illustrate the instructions.
A few notes:
The bass drum pedal is odd, because the 'button' is pressed fairly early when you push down on the pedal. So the sound doesn't occur when your foot fully depresses the pedal and hits the floor (like on a real drum), it happens a little early, like it's reverse-latency. This kind of sucks, and I can't think of a fix unless someone were to write some code to give only that button some latency (I think Harmonix must have compensated for this within Rock Band, because it feels just fine in-game).
There are other programs you can use for the virtual MIDI driver, the keyboard MIDI controller or the Joystick-to-keyboard program, but I tried a few of each and the ones I mentioned worked best for me.
I'm using a brand-new soundcard (E-MU 0404), and after getting the drums working I went in to do some recording in ProTools and suddenly I can't record ANYTHING. It was working before I set up the drums, so I must have screwed something up in the process, only I can't figure it out at all. Sound is getting to my computer, I can see that via my soundcard software, but ProTools is not recognizing it at all. It plays back audio fine, but nothing coming in is registering. It's maddening and I can't figure it out. If anyone has any ideas please let me know. The drums are nice touch, but I need to be able to record.