Just days before Boston Calling was set to open for its second year on City Hall Plaza, in 2014, the festival’s organizers were still waiting on the city for crucial permits — without which the festival would be ruined and the company running it, Crash Line Productions, would go bankrupt.

Then, Boston Calling CEO Brian Appel told jurors in Boston federal court, he got a call from Kenneth Brissette, director of tourism and entertainment for the city — now one of two defendants facing federal extortion charges.

Brissette told Appel that the local stagehands union — the IATSE Local 11 — was upset that Boston Calling hadn’t hired union labor and was planning to picket the festival and set up an inflatable giant rat, and that “this would look bad for the mayor,” as Appel recalled the conversation on the stand.

Appel testified that Crash Line Productions had already contracted all the labor it needed — but that he ultimately assented to hiring eight union stagehands, telling Kenneth Brissette of the decision.

Appel is the latest witness to take the stand in the federal extortion case against Kenneth Brissette and Timothy Sullivan, senior appointees of Mayor Marty Walsh, and accused of illegally pressuring Boston Calling into hiring union labor.

Appel testified to having founded Boston Calling along with partners and investors and to the festival’s success in its first year on City Hall Plaza, in 2013, under the administration of Mayor Tom Menino.

It wasn’t until the summer of 2014, after Mayor Walsh had taken office, that the festival began having problems with permits, he said.

And it was during that summer that Appel had a series of conversations and meetings with Brissette and other City Hall officials – including in at least one instance Timothy Sullivan, who is also charged with extortion – in which Appel was made aware of the displeasure of the IATSE Local 11 over the company’s hiring non-union labor.

Federal prosecutors are presenting their case that Brissette and Sullivan conspired to extort Boston Calling into hiring union labor in order to please their pro-union boss, Mayor Marty Walsh.

But lawyers for the defendants have repeatedly challenged that narrative.

There has been no evidence that Brissette or Sullivan told Appel or anyone associated with Boston Calling that they had to hire union labor, or that there would be consequences for not doing so.

Neither defendant had any direct authority over the permitting process; and Brissette, the “point person” for Boston Calling, had expressed support for the festival many times.

During cross-examination Thursday, Sullivan attorney Bill Cintolo focused on the fact that Boston Calling had been seeking an exclusive long-term lease for City Hall Plaza – and suggested, through questioning, that rather than a case of extortion, the defendants had merely been engaging with Boston Calling in a larger negotiation over a deal that would benefit all parties involved.

Cintolo homed in on testimony by Appel that, upon telling a business partner they would likely have to hire union labor at an unanticipated extra expense, the partner replied that that was “unfortunate, but let’s see if some good can come of this.”

“You understood that to mean, ‘Let’s use [hiring union labor] as a bargaining chip?” Cintolo asked Appel.

“Yes,” said Appel.

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