Thursday's rehearsal moved to the church hall because the school is dark. You posted in the choir app. Twenty people saw it. The three who sing the trio have a concert tonight and have not opened it. On Thursday you will have a room and no trio.
A rehearsal change is a call time. The people who must walk in need the old time, the changed time, the pieces, and a yes that belongs to them.
One call, the people who are called
"Can you make Thursday 7:00–9:00pm at St. Helen's hall, trio on 'O nata lux', call 6:45, yes or no by Tuesday 6pm." That is a decision.
If the whole choir moved, say so, and still write to people one at a time if you need a counted yes. A blast is how you get thumbs and no roster.
Write the old call so a cold singer can see what changed. Write names they answer to, not private nicknames from the section chat.
Set a deadline after work, not during a service. "If I do not hear by Tuesday 6pm, I will ask the understudy and release you from Thursday." A default that assumes silence is attendance is how you cue an empty stand.
They will answer from email
Singers are not connecting an assistant to a community choir. They do not have to. The briefing arrives as mail and a page. They reply from either. You approve the wording. The director's assistant does not speak as the choir.
If you use Claude and an accompanist uses ChatGPT, singers read one package. Their chats stay put.
No season-calendar file. Write the one night. If the season grid already lives on a page the choir uses, name that page.
One person per send when you need a counted yes. Twelve people in a section is twelve approvals of the same ask. Slower than a group text, and that is why the group text fails.
What a sufficient reply is
"Yes." "No — I can do Saturday's extra." "Yes if I can leave at 8:30." One line. Say that is enough. Notes on vowels can wait until they are in the room.
If someone says no, you still have Tuesday evening. That is the point of the deadline.
What this is not
It is not sectional notes. It is not a place to process whether a singer is committed. A no to Thursday is a no to Thursday. If a pattern needs a conversation, have it in a room.
It is not a program change. Dropping a piece is a different decision, with its own ask, after you know who can come.
If your assistant already has the grid, let it draft the change. You read the names and the clock. Then the people who must be there can answer from a phone.