Set up a machine, send one link to everyone, and collect their voices in one place. Play it back all at once.
Birthdays, farewells, a new baby, a friend having a hard month.
Step one · the label
Nobody can play the tape before this date — not even you.
Step two · the outgoing message
Callers hear this before they record. Ten seconds of you explaining what this is beats any instructions.
Dial in
Six characters, from whoever's collecting.
You've reached
Recorded
Your line