“Miss Saigon,” a musical by Alain Boublil and Claude-Michel Schnberg, is a longtime Broadway favorite because it taps into one of the oldest and most pervasive themes of all time: the idea that during our darkest moments, our dreams sustain us and keep us alive.

It’s a powerful part of survival, and one “Miss Saigon” brings to life with spectacular sets, heart-wrenching ballads and a compelling story of war-torn lovers.

When the Lied Center presented “Miss Saigon” Tuesday night, the promise of dreams was enticing, but some cast members didn’t always deliver the full potential of their characters, primarily due to lackluster vocal performances.

The story centers around three main figures: Chris, an American soldier haunted by the chaos of Vietnam; Kim, a young Vietnamese woman who dreams of a better life beyond the civil unrest and sleaze of Saigon; and the Engineer, a notorious club owner who lives to make money off of others. His twisted sense of greed adds humor to an intense plot that involves a romantic encounter between Chris and Kim, their separation, and the fate of their son, Tam.

Alan Gillespie, who played Chris, was earnest in his attempts to convey his passion but often ended up sounding like he was beyond his vocal range during important moments in the show, such as when he and Kim celebrate their love in “The Last Night of the World.” His singing occasionally came across as strained shouting, upsetting his emotional intimacy with Kim during duets, when his voice overpowered hers.

Eymard Meneses Cabling, the understudy who played the Engineer Tuesday, also failed to establish himself as the show’s key comic relief. He was often difficult to understand, and his actions and gestures weren’t strong enough to set him apart from other background characters. But Cabling later regained his ground with solos. He amused and charmed with sly ambitions in “The American Dream,” his exultation of the possibility of profit in America.

Fortunately, there were a few glimmers of light among the dashed hopes of “Miss Saigon” fans who anticipated a more satisfying performance. Laurie Cadevida’s rendition of Kim was lovely; the pure strength of her voice matched her character’s unshakable faith that one day Chris would return for her and Tam. Thuy, Kim’s cousin to whom she was promised in marriage, played by Mario Tadeo, also displayed an amazing voice and strong acting ability. Their exchange in “You Will Not Touch Him,” a desperate moment when Kim must kill Thuy after he pursues her son with a knife, was deeply moving, as was Thuy’s later appearance as a ghost who torments Kim with guilt and bad memories.

Despite occasional shortcomings from key performers who are admittedly talented but perhaps suffered an off night on Tuesday, “Miss Saigon” still glowed with vivid sets, potent lyrics and electrifying drama — and managed to deliver a helping of the kind of theatrical magic that feeds the dreams of Broadway fans everywhere.