It's the standard live-sound/recording quandary: You really need two completely separate mixes. The front-of-house sound at a small-venue live gig will always be heavy on vox and other unamplified items, and light on drums and any instrument that has its own onstage amp. It's always instructive to record the FOH feed for a well mixed live show and listen to it later: all vox, very little else. Unfortunately, to properly record a show, you need to mix everything as if the house isn't there. And a proper recording mix run to the PA with the band thrashing around onstage behind it will sound as much like *dogmeat* as a recording of a proper FOH mix, taken out of context. They are just two completely different animals.
Which will never stop anyone from trying to do it anyway. You can do a few things to help: keep the onstage levels as low as possible. gobo up the drums to keep their bleed down, and try and keep the stage sounds from overpowering your FOH mix. Be extremely careful to position the monitors to allow the polar pattern of the mics to reject everything possible.
If you could somehow get the stage to be completely *silent* acoustically, your FOH and recording mixes would be pretty much equivalent. Meanwhile, the folks who do this for a living do one of two things: either split all the mic and DI signals and use a completely separate mixer out in the truck, or give up and simply hang a separate stereo pair back in the house a little ways and simply record _that_ straight to 2.
I like the latter, myself. That fits with a real-world budget, and lets the sound guy focus on getting the best possible FOH mix, without being distracted by stuff that he can't really properly judge in the venue... It also encourages them not to shove the levels up until the bass-bin cones are popping out onto the floor.
A pair, a limiter set to just handle the worst of the peaks, and a 2-track are a very defensible way to record live in the presence of a PA rig. Otherwise, the sound guy needs 7 hands, 5 ears, and the attitude of a dyspeptic fruitbat- and the paying customers may not be gitting the best possible live show, which is really the key to the biz...
