I've sung in amatorial vocal ensembles and medium sized choirs and there are several professional musicians in my friends and family. Eye contact is very impor

I've sung in amatorial vocal ensembles and medium sized choirs and there are several professional musicians in my friends and family. Eye contact is very important in small ensembles especially when there isn't a director to synchronize breathing and cues with other voices or instruments who share your part, though in a lot of cases you can go by ear just listening to the other parts. In this setting, when there is a director their basic role in a performance is to keep the tempo regular and direct rallentando and accelerando, and to remind you of cues, dynamics, and other things they might've discussed during rehearsals. During rehearsals their role is also to set the mood of a piece of music and get everybody to match it, because obviously if all the musicians have a different idea of how it should sound and feel it's not gonna be a very good performance, and in a concert they can reinforce that mood through body language. In larger choir or orchestra's the director's role to keep the tempo becomes extremely important because you just can't rely on what you hear from the section that's sitting on the other side of the church or of the concert hall; by the time the sound gets to your ears there'll be a few ms of delay and you'll already be primed for starting late, so you have to maintain eye contact or have a "leader" in your section who will do it and to whom you'll refer for cues.