I've looked at the historgrams. I lightened up the image quite a bit and with the D7000 I could've probably lightened it up a bit more. But here's the part I'm struggling with in terms of my photographic learning. What do I do when my meter doesn't agree with what I think the image looks best. I like that the image is high contrast. The first few shots I took I used my cameras meter and it lit up the image like a normal room. But the place was dark, REALLY dark, the lights were harsh and there were harsher shadows. A lot of time I couldn't even see their faces. My question is right now, do I trust how "artistic" intuition or do I trust my light meter?
I first noticed this dilemma when I was just screwing around with my camera in my room. I turned off all the lights except for my TV. Then I used the light meter to set "proper" exposure. I put it on a tripod and aimed it at an object. It took 30 seconds for proper exposure (oh yeah, this was in the dead of night so the only light was my TV and at ISO 100, since well, nothing was moving in the room, I'll take as little noise as I can). When I looked at the result, it looked like I had my lights on. Which is not at all an accurate representation of what the image should've looked like. At least in my mind. In my mind, in that situation, it was not the proper exposure.
I usually don't shoot in those kind of lighting conditions, but I do know from experience that they can be tough. Your meter only knows what it can see. It's only going to look at shades. Your metering mode is very important. Do you happen to know what metering mode you were in? If you don't, chances are, you were in matrix, which means the meter is going to take an average of the entire scene and make the exposure average out to middle grey in tones. From what I see of your histo, using the somewhat useful, but not quite that accurate Firefox histogram plug-in, it seems it metered you where it was because there were lots of shadows, and lots of highlights. Mid-tones weren't really present. You really clipped a lot into your shadows. Basically, your histogram was opposite what the "model" histogram would look like. Typically, most of your data should be bunched up in the center, with it tapering off at the ends. The "model" histogram will look like the traditional bell curve we all learned to love in statistics class.
So what can you do? There are a few things. First is switch metering mode. A more limited meter mode might be more helpful. Spot or Partial (sorry, can't remember if they have a different name with Nikons, I shoot Canon) would allow you to focus on a specific spot, or small area to get a proper exposure. Which to use is going to depend on the situation, and what you think will give you better results. That will come with experience. It might be a good idea to play with the different metering modes in different lighting situations in order to see what they do. Another thing you can do, if you know that the lighting for the scene is (or will) trick your meter is to use exposure compensation. In this one, you could likely use +1 EV safely, and maybe up to +2. Keep an eye on your highlights though. In those scenes, the bright areas will likely get blown out.
Like e.rose has mentioned, the lighting really sucked there, and that just makes it even more difficult. Next time, try the techniques I mentioned, and focus on getting your exposure correct. If you can nail exposure most of the time, they start focuing on other things. But if your exposure is off, you won't be making good photos. Also, listen to e.rose. She shoots bands all the time, so she'll know a lot more about the acual technique for doing it than I will.
EDIT:
Here's a screencap of one of your shots with the histo next to it. You can see what I mean. Your histo has about 85% of it's data in under 10% of the tonal values. This means you are almost certainly underexposed. In certain types of photography (low key, for example, which your shot isn't) this could be an acceptable histo. But not for the shot there.