Word for "a group of people responding in unison to a greeting" [closed]

I'm looking for a word to describe the event in which a group of people respond in unison to a greeting or introduction.

The most obvious example I can think of is in an Alcoholics Anonymous meeting, when a person introduces themselves and the rest of the group responds in unison with the same phrase.

Another example might be a customer entering a restaurant and the employees all greet the customer with the same saying.

The best word I could use to describe this is a "reprise", but I don't think it's commonly used this way.

Edit: An example of a sentence of how I would expect this word to be used might be:

John expected a reprise after introducing himself to the group for the first time, but all he got were stares and murmurs.

Solution 1:

Chorus can be used to refer to a group of people saying something in unison

Example:
"Hi everybody!" said Dr.Nick,
"Hi Dr. Nick!" the crowd responded in chorus