I agree. Choir rehearsal should be a time to practice and sings songs that have been prepared prior to rehearsal by leadership. It is also a time that should be managed by one person, IMO. Without the presence and acknowledgement of a person to have the "final say so", you will likely have chaos and lack of direction regardless of what rehearsal system you choose. Just curious, who makes decisions before and during a typical choir rehearsal? Also, who makes decisions during service if something has to be changed?
You are absolutely correct. Without the one person who is "in charge", you will have nothing but experience. Learned from experience. I'm not sure what your position within the Music Dept. is, but in my experience, its always been the MOM, who would just happen to be either the director or musician, if there is any questions regarding the choirs, the conduct of rehearsals, the structure of rehearsals, it should go through them. There needs to be a meeting where this position is assigned, whether it be the director, or musician or whoever, and whoever it is assigned to needs to go to the rehearsal and basically start laying down ground rules for how things are going to start going.
Let them know that you are in charge, and things are going to start being in decency and order. You make the final say, and thats that. Anything regarding the Music Ministry during rehearsal or service goes through you, and thats it. Those who are used to having their way might get upset, and if they end up leaving, then maybe its for the better of the ministry. But people will grow to respect the effort over the long run, and are more likely to fall in line if there is stern leadership up top. People need to recognize who is in charge and that person also needs to be consistent with what they do. Then and only then will things begin to be accomplished.