I have been listening to class B go-around ATC recordings. After the initial climb of the go-around, the tower gives the flight a heading and altitude. Then, on some recordings I hear the tower say "contact departure" and a frequency. But on others I don't hear that.
I can't tell whether:
It's optional for the tower to hand off the flight to departure in a go-around and the tower can keep control the whole time until they land, or
The tower always switches the flight to departure, but sometimes that hand-off is left off of the recording.
Which is it?