|September 17th, 2012
I would encourage you to do this too, but you should know: you probably won't like how you sound. While some of this is inflated expectations, people also generally think they play better than they actually do. While discovering how you actually sound can be sobering, I do think the learning it enables is worth it.
If you're willing to take the ego hit in exchange for becoming a better band, here's one way to start recording yourselves. Once you're used to it you'll find it only adds a couple minutes to your setup time. You do need a few things:
- A laptop with an input jack on which you can install Audacity.
- A friendly and cooperative person running sound.
- An extra aux output on the sound board.
- A 1/8" TRS to dual 1/4" TS cable. Like this one. It will look like a Y-cable connecting two large plugs to one small one.
When you get to the dance you ask the sound person if they might have an extra aux output or two that you can use to record yourselves. Most of the time they'll say yes. Plug the small (1/8") end of the adapter cable into your laptop and give them the two big (1/4") ends. If they have two auxes you can use both of them and record two tracks, otherwise they should just plug in one at random and you can record a single track. Start Audacity on your laptop and tell it to record from "line in" or "external microphone". Ask the sound person to give you equal amounts of each of your instruments, but not the caller. If you have two tracks to work with, divide the instruments among the tracks. For example, in our band with fiddle, mandolin, and piano we put the fiddle on one, the mandolin on the other, and the piano on both. The goal is to give yourself as much flexibility as you can later to make instruments louder or softer. 
With people playing you should now see that the computer is picking up sound. If the squiggles are big and getting truncated on the top and bottom then the input is too high and you should ask the sound person to turn it down. If it's very small you should ask them to turn it up. If you have time you can listen to it some and decide whether to turn various instruments up or down in the recording mix, but if the sound person sets their initial gains in the usual way it should be roughly correct even without checking.
At the end of the night, save as a "wav" file. Then in the car home you can connect the laptop to the car's stereo and listen back to it and talk to each other about your playing. If you recorded two tracks, in Audacity you want to use the split stereo track to mono feature and then use the volume controls for each track to turn them up and down. Otherwise the people on the left side of the car hear lots of some instruments while the people on the right hear others.
Let me know how it goes!
 The ideal would be multitrack recording, with each instrument being recorded completely separately, but this requires a special board that can send all those tracks to the computer. Audrey's board can do this, and we've recently started doing it that way, but for a long time we were just recording one or two tracks.