BOSTON (CBS) — Security is a top priority as the city prepares for the 4th of July concert rehearsal Monday and Tuesday’s big event.

Boston Pops and city officials estimated that about 100,000 people would turn out Monday evening to see the rehearsal for the 4th of July show.

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“The atmosphere is still as good as it is on the Fourth. People are just as happy tonight as they will be tomorrow,” one spectator said Monday night.

Some attend the rehearsal because they care about the music more than the fireworks.

Others have devised a plan to see the best of both.

“I love to see them rehearse because then the next morning I come very early and I stake a spot by the river to watch the fireworks the next day,” Mary Ann Rollings explained.

Police boats on the Charles River. (Photo credit: WBZ-TV)

Police officials said they would have eyes from the sky, from the water, around the event, and in the crowd, working to keep spectators safe.

Security is playing a significant role in those preparations, with police boats even being deployed on the Charles River. Law enforcement officials are confident their plans for the 4th are solid. State Police Colonel Richard McKuen says law enforcement will be ready.

“We will deploy a multi-layered, multi-agency security plan to maximize the public’s safety,” a State Police officer said.

Officials also stressed that there are not threats to the event right now.

The State Police are also asking people coming to the events to report anything that looks “suspicious.” They’re also urging prospective show-goers to find out what is and is not allowed on the Esplanade.

“It’s specifically designed to keep dangerous items out of the venue and to aid in the speed of screening so we can get people in as efficiently as possible.”  State Police Major Rick Ball said.

Large objects like coolers on wheels or backpacks are not allowed.

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Spectators on Monday waited patiently in line.

“We read the rules so we didn’t have any trouble getting in once we got to the front,” said Megan Fountain.

Joshua Ruman commented, “Anytime when you wait in a line you get frustrated, but you are here for a fun event so you have to have a good attitude.”

The set-up at the Hatch Shell. (Photo credit: WBZ-TV)

Even before Monday’s rehearsal, hundreds were out trying to get a sneak peek of the preparations over the weekend.

“The set up, it’s legendary,” onlooker Roufun Kwon said.

Vivian, a long-time Boston resident, said she never wants to miss a performance.

“I’ve sat here through the hottest days, misting, you know, the mists, all of that, I’ve done it. You can’t be from Boston and not do it,” she said.

“I just want to catch some of the festivities,” another spectator said.

The event includes the “1812 Overture,” a part of the event that requires “heavy artillery.”

Keith Lockhart is leading the Boston Pops in Monday’s rehearsal and Tuesday evening’s show features some of the country’s most famous voices. Pop singer Andy Grammer, folk singer Melissa Etheridge, Hamilton cast member Leslie Odom, Jr., and Tony Award-winner Brian Stokes-Mitchell are in the line-up.

The event is expected to draw a half a million people by the time it’s over Tuesday night.

WBZ NewsRadio 1030’s Carl Stevens reports

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