OK. I see what you are trying to achieve. Correct me if I'm wrong. Even in live situations, recording would still be achieved through the mixer, which comes directly out of the instruments/guitar amps. I don't think people would try to record directly out of the main speakers.
And if you want to "decrease" the definition to simulate a live effect, there are several ways around it, I think. Most of it would be during the post-recording phase, after you've already got all your materials recorded. You can add plugins. Most, if not all the amp simulation plugins, are for guitars and basses. You'll never find any for keyboards for the reason I gave above. You can try to put your keyboard recording through a guitar amp simulation plugin. But I don't think that will actually create a "live" effect - it will just make the keyboard sound bad. And keyboardists will NOT like it if you change their sound too drastically. We choose our equipment carefully - hence why there are people who swear only by Korg, or Nord, or Roland, or Yamaha, or various softsynths. We want the sound to be exactly like it.
The other is to add a general reverb to the mix, giving the effect that you're recording in a large hall. I would be careful of this though - too much and you get a mess.
The other way is to introduce noise - background noise. I've got a collection of ambient noises including basic ambient large concert hall "empty" sound to noises made by people in a concert - from coughing to cheering/clapping to noises made by concert musicians (page flipping, chairs shuffling etc). I don't think we should overuse these, though.
Other than these, this will be a question for recording engineers to answer.