The room was more cavernous than an airplane hangar, but Anthony Hamilton tried to make it feel like church.

As the North Carolina R&B singer delivered a gospel rendition of his 2008 song “Fine Again,” his rough-hewn tenor soared through Hall E of the Washington Convention Center on Thursday night at a concert celebrating this week’s Martin Luther King Jr. Memorial dedication.

But as Hamilton pushed the song higher, the mood still felt a little down. Moments before the performance, organizers announced that Sunday’s dedication festivities on the National Mall had been canceled in preparation for Hurricane Irene. Meantime, a scheduled Thursday night performance from Anita Baker had been nixed. And when the concert began, there were more empty seats in the room than people.

So for the next two hours, gospel and R&B stars past and present did their best to fill the place with joyful noise, including Patti LaBelle, O’Jays veteran Eddie Levert, India.Arie, the Impressions, Naturally 7, Nolan Williams Jr. and the Voices of Inspiration choir — all backed by musical director Ray Chew, who leads the house band on “American Idol.”

There were some big names in the audience, too. Jesse Jackson, Cuba Gooding Jr., Michael Eric Dyson and Jackie Joyner-Kersee were all recognized from the stage by actor Wren Troy Brown, the evening’s emcee.

The concert, dubbed “The Message in the Music,” promised songs from the Civil Rights era, but the evening’s younger artists chose to look forward, treating King’s legacy like a living, breathing thing.

Arie was joined by Israeli pianist Idan Raichel, on a collaboration she called “the embodiment of the dream.” She dedicated the performance to her late grandmother, who attended the March on Washington, and sang a new song called “Open Door,” encouraging religious tolerance and marriage equality. “Can we give up the need to be right?” Arie sang. “Give the world a present/Give the gift of your acceptance.”

Where Arie was focused, Naturally 7 was quirky. The a capella septet beat-boxed and harmonized through Burt Bacharach’s “What the World Needs Now” like seven Bobby McFerrins. When King’s voice seeped into the mix, it was hard to tell if it was a pre-recorded sample or a masterful act of ventriloquism.

Levert had the crowd on its feet late in the concert, sweating through the O’Jays classics “Give the People What They Want” and “Love Train.” After going through the motions all night, Chew and his band finally came alive, sinking their teeth into the vintage rhythms.

They may have been warming up for LaBelle, who closed the show see-sawing between grandiosity and grace during “Two Steps Away” before offering a volcanic take on “Somewhere Over the Rainbow.”

Between her biggest, highest, loudest notes, she offered condolences for the late Nick Ashford, encouraged tolerance and asked for the safe return of U.S. soldiers fighting overseas.

But those heartfelt sentiments didn’t come without a little showboating. LaBelle was only onstage for two songs, but found time to change from high heels to higher heels and primp in front of a hand mirror. At times, she would step away from the microphone and wail at the top of her voice.

You could hear her in the back of the room — a room longer than a football field. You could probably hear her over the rainbow, too.