For Tuckwell, who is resigning from the symphony, it would be his last appearance. He has conducted the orchestra at Antietam since the event began a dozen years ago.
"It will be a nostalgic and emotional thing for me," he said of Saturday's concert.
From a physical standpoint, Tuckwell said standing on an open-air stage in summer has its drawbacks.
"Sometimes it's too hot. Sometimes there are too many bugs," he said. "But tonight should be the best weather we've ever had. And from the emotional side, to look out at that sea of people ... it's great fun. It's wonderful. I love it."
Tuckwell added that when the cannons go off during the "1812 Overture" each year, the sound is powerful and the fumes - depending on wind direction - can be overpowering for orchestra members.
As Tuckwell went over his music, battlefield Superintendent John Howard and his son Bryan were looking out over the crowd picnicking on the grass at Antietam.
"We spend most of the time walking through the crowd, handing out programs, garbage bags - whatever they need," Howard said. "After it's all over I take off this hat and we start picking up garbage. Last year we had it all cleaned up within two hours, and it didn't even fill two dumpsters. I don't know if they're eating the Saran wrap or what, but it isn't ending up in the dumpsters."
Howard said the Antietam celebration is a family-oriented event not tainted by commercialism or crime. He said the only arrest in connection with the celebration was a driving under the influence arrest three years ago.
Howard said this year's event was being staffed by 50 volunteers and 99 professionals - including police, REACT members, fire police, rescue and fire personnel and rangers from Antietam and nearby national parks.
Howard said the National Weather Service called for clear skies and a temperature of 75 degrees at concert time. The temperature would drop into the 60s by the time the program closed with a fireworks display by Zambelli International, he said.
The forecast was good news for Mike Sokol, an independent acoustic engineer working under contract with MHA Audio, which was handling the sound system for the concert. Sokol was calibrating a stack of speakers just outside the Visitors Center. There were 10 stacks of two to six speakers each at several points on the battlefield. They would broadcast the music to the crowd on a time-delay basis, depending on the distance of the speakers from the stage, Sokol said.
Sokol said the speakers he was working on were 600 feet from the stage.
"It takes six-tenths of a second for sound to arrive here from there, so I have to make sure this is set on a six-tenths of a second time delay," he said.
Proper timing would eliminate the echo affect that can make concerts sound chaotic, he said.
Wind and temperature could affect the time-delay settings at concert time, Sokol said. Probes in the system would automatically compensate for temperature, which can affect the speed at which sound moves through the air.
Sokol would just have to stay alert for wind changes that could force him to make on-the-spot adjustments.
"I'm basically listening and tweaking," he said. "If something goes wrong, I scramble."
As Sokol was checking the speakers, Mike Scarfe of MHA Audio was working the sound mix for the symphony on a console near the stage. He was communicating with technicians who were checking mikes set up for each of the symphony members' instruments.
It had taken Jeff Garretson and nine others from National Events of Virginia eight hours to erect that stage. Garretson said it would take six hours to tear it down.
To the left of the stage members of the Maryland Army National Guard were moving six105mm Howitzers into position. The guns would go off on queue during the playing of the "1812 Overture."
Lt. Clay Allison said the howitzers, which were loaded with blanks, have a range of seven miles when live shells are fired.
During the real Battle of Antietam, 500 cannons were being fired by Union and Confederate troops at the height of fighting, said Seasonal Park Ranger Al Fiedler. As he looked toward the mountains on the horizon behind the concert stage, Fiedler said, "Can you imagine how they must have echoed off the windows of the homes ... off the mountains. What a sound that must have been."