A lot of people have asked me whether or not to use reverb in a live situation. As always, my answer is to do what your ears tell you to, but here’s my opinion:
If your show is in a small (500-2000 seat) theater which was designed for plays, you may actually use a good reverb with excellent results. If, however, you are in a larger venue, usually the last thing you want to add is more reverb. In cases like this, I would be more inclined to use a very slight amount of a short delay. It sort of achieves the same result – that of adding some ‘space,’ but tends to not muddy things up quite as much. If you’re mixing an outdoor show, you can use reverb, but I find that it kind of sounds like it doesn’t belong. I suspect this is the psycho-acoustical aspect: your eyes see no reflective boundaries, and your ears don’t hear any reverb on any other sounds in the area, so a bunch of reverb on vocals or drums in your mix sound out of place.