>Actually, it's the middle of the night. All the exterior >lighting is incandescent and streetlights.
Right . . . but it's still coming through the window blinds in shafts next to the drummer and adding more soup to the already difficult and dim lighting.
>Here is another example taken at the bar on the far side of >the room. Not much of a shot, but shows the problem.
It sure does, and probably makes the best possible case for picking shooting position, doing a custom white balance, then firing away. Change the shooting position, then take another 15 seconds or so to do a new custom white balance, then fire away. The relatively few seconds it takes photographers to do a custom white balance in these sorts of shooting conditions will save literally hours of labour in post.