I think Lt. Bob has the handle on the non computer way to match the 2 beep. Especially if you can line up the waveform to the same point by shifting or sliding it around. Since I don't have a hardware based hard disk recorder like the Roland, etc, for me it was just a matter of putting the tracks side by side and lining up visually to the cursor (play line). If you need to check it you can play them back panned or mono and see if you hear an echo. When they are lined up properly, you should hear no echo when you play both. If you are off by a sample or two, it probably won't make much if any difference for most things.
The idea of the two beep is one I borrowed from film scoring. Editors would ask for a beep 2 seconds before picture start. They would align the track based on that beep and everything matches picture just like you intended when you scored it. When Lt. Bob and I decided to try to collaborate, he asked how we could stay in sync. I said I'd put the 2 beep as a cue on the track I send him and for him to copy that beep on whatever he sends me back.
You could do the same thing with a standard four count as long as it doesn't bleed over into the intro of your song. The way we did it gives us two seconds of silence before the track starts, which is kind of nice.
What Lt. Bob did was send me a stereo CD of my bed track and his sax. The track I sent him was panned left and his new sax was panned right. Here is how I got his sax.
1. I imported his track from the CD into Digital Performer.
2. I lined up his track to mine using the beep
3. I panned the stereo track he sent me completely right so that all I heard was the sax line--none of my guide track.
4. I bounced that stereo track as a mono track, using 3.5 db of attenuation.
Final result was his sax track alone as a mono track--in sync with the other tracks on my computer.
For you guys who record to computer, you are probably saying "Hey! I could have just added that 2 beep to a mono track or stereo track and sent it that way, which would be simpler. Thats true! I don't know if you can do that kind of stuff on a non computer hard disk system though, since I don't have one.
Anyway, its encouraging to see that there are ways to do joint projects. What I think would be fun is to write something, make a simple guide track, and pass it around--have one person play keys, another bass, another drums, etc. Then, assemble all the parts into one final master! In fact, we gotta do this!