Half the actors onstage are singing “Open up a window.” But an equally vociferous group disagrees, intoning “Too many flies.”

Through it all, John Adams loudly pushes the cause of independence from Great Britain, while others try to shush him with “For God’s sake, John, sit down!”

That’s how the musical “1776” opens, with a song that depicts the Second Continental Congress dealing with the sweltering heat in Philadelphia 250 years ago.

“The show is true to life. It tries to show you these are real people,” said Adam Randis, director of the production, which Pennsylvania Theatre of Performing Arts (PTPA) will present July 3 through July 12 at 212 West Broad St., Hazleton. “They crack jokes. They argue and disagree. And they try to find common ground. We don’t see that so much anymore.”

A history professor at Luzerne County Community College, Randis calls the musical “the show of my soul.”

He appreciates the way “1776” tells audiences about a pivotal time in our nation’s history, during which Thomas Jefferson wrote the Declaration of Independence, the sage-like Benjamin Franklin gave the not-so-popular John Adams tips on how to deal with people, and delegations from all 13 colonies eventually voted “yes” for independence.

“Adams is the driving force,” said Randis, who has played the fiery lawyer from Massachusetts himself in past productions. “You need a real dynamo.”

Playing John Adams this time around is Ciarán R. Burke of Scranton. He describes the character as “very strong-minded and strong-willed. He can be abrasive. He doesn’t have a lot of patience for what he sees as nonsense.”

Fortunately for the cause of independence, Adams has friends who are not as, in words from the script, “obnoxious and disliked” as he is.

“Franklin has a tempering influence on him,” Burke said. “Everybody likes Ben Franklin.”

Dave Zimmerman of Lehighton, who portrays Franklin, agrees. “If anybody could spend a day with one of the Founding Fathers, people would pick Ben Franklin,” he said. “He’s not straight-laced. He sees life with humor. He tells Adams to relax.”

Adams is also grateful for support from his wife, Abigail, hundreds of miles away in Boston. Excerpts from the real-life letters the couple wrote to each other are interwoven into the “1776” script and song lyrics

“He holds her in such high esteem,” said Kit McElvar of Lehighton, who plays Abigail. “He would talk to her about everything and seek her advice.”

McElvar’s research for the play included reading in their entirety many of John and Abigail’s letters, which she found online.

Other actors have prepared for the show in different ways.

Jonathan Mosebach of Bethlehem, for one, has been “brushing up on my Gaelic accent … listening to Irish music and watching the Tartan Army at the World Cup” for his portrayal of Col. Thomas McKean, one of three delegates from Delaware.

“Delaware was a microcosm of the country as a whole,” Mosebach said. “Because the delegates were divided on the question of independence, and so was the country.”

As for Geary Gorup of Fleetwood, he plays McNair, the Congressional custodian, “as if he’s slightly hard of hearing. He was always ringing the bell for years. I thought that would have made him slightly deaf.”

While McNair was not a voting member of Congress, Gorup believes he would have been on the side of those who wanted independence. So, while the script calls for McNair to join in the harmony for a number called “Cool, Cool, Considerate Men,” in which the conservative faction of the Congress disdains Adams’ ideas about independence, Gorup said, “The only way it makes sense to me to have him do that is for him to do it in a mocking way.”

“Cool, Cool, Considerate Men” includes some stylized court dancing, and is one of a wide variety of musical numbers in the show.

Some are haunting, Randis said, pointing to “Mama, Look Sharp,” in which a young courier conjures images of mothers finding their soldier sons dead when they didn’t come home to supper.

Others deal with such serious subjects as slavery and the evils of a trading triangle that involved molasses, rum and human beings.

And some, like “The Egg,” are pure fun. In that one, Jefferson, Franklin and Adams explain why they, respectively, prefer the dove, the turkey and the eagle as the national bird. While they’re at it, they compare the heat of Philadelphia to an incubator for a baby bird in an egg.

“And, just as Tom here has written,” they end up singing together. “We say, to hell with Great Britain. The eagle inside belongs to us!”

Show times are 7 p.m. Fridays and Saturdays (including July 4) and 2 p.m. Sunday through July 12. For the final weekend, there are dinner and show options, with Saturday’s dinner starting at 5:30 p.m. and Sunday’s dinner at 12:30 p.m. Dinner reservations for July 11-12 are due by July 6.

Tickets for all performances are available at ptpashows.org, and show-only tickets will also be available at the door beginning one hour before curtain.