Being a single operator with no staff, it falls on me to make sure all facets of the ceremony are worked out in advance. Most of my clients don't hire a Coordinator; hence, I assist in that regard. So, you've never worked a Rehearsal? Most of mine have been outdoors and at a separate location or distance from the reception location. If the Bride does have a Wedding coordinator, most of my work is as you say: show up, play the music for seating of guests, processionals, and make sure the Minister's mic is working. I forgot to mention. If the Ceremony calls for a soloist to sing the bride's processional, it helps to have a practice session the day of prior to start or at the Rehearsal, day before. I don't like surprises that can be prevented in advance.