Classical music will return this summer to the Mann Center, albeit in a diminished state. The Philadelphia Orchestra, which once played an 18-concert series in Fairmount Park, and more recently nine, will perform six this summer - and only three can be considered purely classical.

The season will open June 23 with fireworks and Tchaikovsky. Cristian Macelaru will conduct the Romeo and Juliet Fantasy-Overture and, with cellist Hai-Ye Ni, Variations on a Rococo Theme.

Nino Rota's score to The Godfather will be performed June 25, as the movie is shown on two new video screens. A new audio system promises better orchestral sound for picnic-goers on the lawn. Justin Freer will conduct.

An all-Gershwin program will have pianist Terrence Wilson on June 26, with Macelaru leading the orchestra in An American in Paris and, with vocalists Taylor Johnson and Norman Garrett, songs from Porgy and Bess and other works.

The Baltimore Symphony Orchestra will take over July 18 with Seth MacFarlane crooning not the theme songs from his shows Family Guy or American Dad! but American Songbook standards.

The Philadelphia Orchestra will return July 23 in a Lord of the Rings program, July 24 with pianist and singer Diana Krall playing pop standards, and an all-Beethoven concert July 25. An as-yet-undetermined orchestra will perform a Legend of Zelda concert on Sept. 18: "Master Quest."

Mann leaders say they continue to offer the Philadelphia Orchestra a standing invitation for music director Yannick Nézet-Séguin to make his debut at the West Philadelphia venue. As for the orchestra performing just two weeks this summer instead of the recent standard three, Mann president and CEO Catherine M. Cahill says: "We were always open to having them for more than two weeks, and hope that they will once again avail themselves to three weeks."

Orchestra executive vice president Ryan Fleur says, "The orchestra is hopeful that the stars are going to align for Yannick to be at the Mann." But, he says, the orchestra must wait for the Mann to book pop acts first, "so the orchestra schedule falls in behind that." The conductor's schedule is booked years in advance, he said.

In fact, says Cahill, the Mann considers the orchestra to be "its top priority, and will continue to work with the orchestra to ensure that managing the calendar meets their needs, as we understand that orchestras book far in advance of the pop world."

Asked whether he thought it was important for Nézet-Séguin to perform at the Mann, Fleur declined to answer, offering only: "It's important for Yannick to have a relevant presence in Philadelphia throughout the year."

As for the orchestra's continuing modest presence at the Mann, Fleur said that "given how the orchestra season currently aligns with Vail, Saratoga [Performing Arts Center] and the vacation weeks, there's a limited amount of time the orchestra has in the summer." He said the orchestra had not scheduled Verizon Hall concerts this summer, as it did last year - a move that the Mann considered competition.

Cahill calls the Baltimore Symphony a "fine orchestra, and very flexible" about artists and repertoire, and says the Mann is in conversations with the group about developing a long-term relationship, even as it pursues a multiple-year contract with the Philadelphia Orchestra.

In the meantime, the Mann continues to develop its pop roster, with guests this summer such as Brian Wilson, Barenaked Ladies, and Phish. Although these concerts bring audiences, they are hardly lucrative for the Mann. "The margins from pop programming are very lean," Cahill says, "even in sell-outs, because artist fees are significant - shockingly significant, in some cases."

But with government, foundation and individual support, the Mann is growing its artistic muscle, holding master classes throughout the city - with jazz performers Al Jarreau, Chris Botti, Uri Caine, and Terence Blanchard - and this summer will once again mount a festival with a social-message purpose. As a follow-up to last year's Philadelphia Freedom Festival, the Mann has programmed seven events between May and September under the banner of "Liberty: Unplugged!"

The festival will happen at the Mann but also at other venues, making the Mann a little bit more a producing organization and less just a venue. "Liberty: Unplugged!" explores three men and three anniversaries - Frederick Douglass, the Rev Martin Luther King Jr., and Nelson Mandela, and the 150th anniversary of the ratification of the 13th Amendment ("Neither slavery nor involuntary servitude . . . shall exist within the United States . . . "), the 50th anniversary of the passage of the Voting Rights Act, and the 25th anniversary of Mandela's release from South Africa's Robben Island prison.

The first event, May 2 at Mother Bethel A.M.E Church at Sixth and Lombard Streets, will be a free concert in collaboration with Play On, Philly! and the Philadelphia Youth Poetry Movement. Among the works on the program will is Hallelujahs of the Free, commissioned by Play On, Philly! from Philadelphia composer David Carpenter. Scored for speaker and orchestra, it uses a collage of texts from various Douglass writings, but mostly from his speech "What to a Slave is the Fourth of July?"

Putting Douglass, King, and Mandela together works thematically, "given that these are three men whose movements have changed the world and whose messages have still such resounding significance," says Nolan Williams Jr., CEO of NEWorks Productions and artistic director of the Mann festival.

"When you look at the focus of their movements and look at what's going on in the world now, it makes complete sense - Douglass in combating slavery, King in voting rights and Mandela in apartheid. In our present time there is a need to combat modern-day slavery and human trafficking, the need for voting rights, and the push for human rights. These are very relevant and present discussions I think we need to be having."

A poetry contest, in-school programs, a free "Three Kings" concert in August and a "Twitter Town Hall" in the fall are all in the lineup, details of which are still falling into place. Cahill says part of the goal is to bring in residents of the Mann's own neighborhood "who never felt the door was open to them."

Says Williams: "Music is arguably the only universal language. When you think about the power of bringing people together, you may not be able to get them to sit down together. But, boy, tell them we're having a concert and they'll come. And you have a chance to reach everyone."