One day last fall, employees of Iron Mountain, a Boston-based records management company, were subjected to what union organizers like to call a captive audience meeting.

Employers hold these anti-union meetings once they’ve gotten wind of an organizing campaign in their midst. Whether the meeting is led by in-house managers or outside consultants, the gist is usually the same: Joining a union is totally your call. But it’s a really bad idea, and we’re disappointed it’s come to this.

The spiel at an Iron Mountain facility near Atlanta, where the Teamsters were trying to organize truck drivers, wasn’t unlike the anti-union speeches commonly delivered at other companies. What made this meeting different was that a pro-union worker in attendance was surreptitiously recording it.

“We have the right to educate you,” the Iron Mountain manager lectured his employees. “And we’re going to exercise that right.”

Read more and listen to the recordings..