Just my two cents on the issue, I´m not really a taper person, recording acoustical classical music.
Well, of course everyone tweaks the recordings. You select microphones, you place them in the room and in relation to each other, you run them through your favourite preamp, and through your AD converter. Each of these modifies the sound some way. Setting levels is one way to compress things, many of the boxes compresses a bit towards 0dB full scale and many limits so you will not get digital distortion when going above 0dB.
So once at home I do postprocess. The originals are of course archived.
I always add gain as I never allow levels to get close to 0dB FS when recording. I don´t like the sound of my equipment close to full out. Generally I add different amounts of gain to different parts of the show - a very quiet piece might get a little more to pull it up a little, applauds often gets a little less gain as the mics often stand among the audience.
Genarally I remove the dead time between movements and between pieces. Fade-ins and fade-outs of the room noise instead of instantly going from digital black to room noise. In between movements I tend to add a bit of room noise instead of going to total black.
Often a highpass filter, which may vary during a concert. Perhaps a bus passed and the very low frequency noise of that can be removed just there as no bass instruments played just then. I like to decrease audience noise as well, coughing and squeeky floors, paper rustling and things dropped or doors closed. Just reduced enough to not be the main attraction anymore.
So once all this is done, it might take a slight bit of other tools. These are difficult to use and easy to abuse. Here I´ve come to rely on my monitors and headphones and mostly on my ears but this is the part where I thread real carefully. Less is more and real carefully are the words.
Things that may come in are very slight EQ changes, most often 1 or 2 dB down, rarely more. Some of my mics has a rise in the high frequencys to compensate for far-away recordings that I like to temper a bit. Sometimes the room has very pronounced "modes" or tones that it likes to amplify. This might come from mic placement, example is that sounds may bounce on a hardwood floor or walls and amplify a few frequencys. At most a few dB-s down to decrease the problem but not to remove it. Less is more.
A very small amount of reverb sometimes is what the recording requires in order to be enjoyable. Just enough to make the room less dead, but never enough to be heard. Preferrably this should have been done at the recording by having an extra set of reverb mics further back in the room or by moving the main mics, but when recording with an audience to two microphones this is not always possible.
Finally, on a select few recordings, a very small amount of compression on the stereo bus. Setting on the compressor to a ratio of 1.1 or 1.2, extremely small compared to most other usages. It can sometimes melt together sounds but it may as easily destroy more than it saves.
Anyway, your choices will vary, but no recording is totally faithful -- it always has inherent choices. Electing to not post-process means that you are more limited in how to record in the first place, which may be a good thing from some aspects but not always. It will probably force you to go what I think is too hot into the preamp / AD which creates "distortion" (meaning modifying the signal).
Gunnar
