Piper your correct in your comment and sorry if we got off track with this one. The problem you are experiencing is that the voicings of everything except the bass are in conflict on the frequency spectrum so you are going to need to do a little eq tweaking so bring out everyone clearer in the mix. I would recommend if you have eq's on your board with adjustable Q's (bandwidth) to set your Q at a wide level say 2 or so and then boost it about 10 db or so. Have each person sing/play individually and sweep the eq up and down until you find a spot where that particular vocal or instrument seems to be most present in the spectrum. With voices it is going to be difficult to find a whole lot of difference between the two. Once you find the sweet spot you can tweak the eq for each one to a different level or you can cut a bit. Say you find that one of the singers vocal hits really good around 250hz or so then you can boost that person there and cut the others in that area. You will want to lower your Q before doing that. When we talk about Q the amount of bandwidth (frequency range) that is cover is inversely proportional to the number. i.e. a Q of 7 would cover less ground than a Q of .5 this is easily displayed if there is any kind of a parametric representation on your board. I don't want to get too deep. This could be done as easily as just bringing the guitar down in the mix so that it doesn't compete volume wise with the vocals and then boosting each vocal in a different frequency range to give them their own spot in the spectrum. You could also try panning each vocal slightly off center and opposite of each other to bring them out as well, say one at 11 o'clock and one at 1 o'clock.