There is often tension between the two parties and tension is the last thing you need on a Sunday morning when it is time for the worship leader and the worship team to lead everyone into the presence of God. I would guess many of you, who are reading this, are nodding your heads in agreement right now.
I feel the first step in making sound checks and rehearsals run smoothly is establishing who is in charge. This can be determined by whether you are having a “rehearsal” or a “sound check”. There is a difference. The rehearsal is for the musicians to learn and go over their parts and the sound check is for the soundman to set levels and EQ’s etc. The rehearsal should be run by the worship leader and the sound check should be run by the soundman. Now in all fairness, most of us combine the two into one event. Understanding that there are two things going on is key. The soundman needs to make sure that the musicians are comfortable and can play and sing their best, but the musicians and worship leader must remember that the soundman is responsible for making sure all the people in the sanctuary can hear well.
Being a soundman requires technical skill, a good ear, and a lot of people skills.
You can try to explain to musicians that the monitors greatly affect the sanctuary sound. Turn the house off and have the worship leader sit in the congregation and listen to the sound in the room coming from the monitors alone. This may help him/her understand the challenge.
The bottom line is that the pastor has the last word. If there is conflict, try to educate all involved and then determine who has the last say and go with it. If the worship leader understands the issues and the challenges and he/she is in charge, go with it. If you run into feedback problems, do all you can to eliminate them and then communicate your limitations to the one in charge.