The Three Tenors with boy-band looks, singing The X Factor's karaoke songbook: the equation Simon Cowell made to arrive at Il Divo seems simple enough. Thirty million album sales later, the sum adds up, commercially. But for the three thirtysomething opera singers and one minor French pop star who answered Cowell's latest talent search, something rings hollow. The opera men – American tenor David Miller, Swiss tenor Urs Buhler and Spanish baritone Carlos Marin – were established singers, committed to honing their art, before being able "to pay my rent for a year", in Buhler's words, diverted them. That was five years and four albums ago. Il Divo is their artistic life now: operatic vocals shorn of opera's epic emotional sweep, but gifted with a huge audience. Unlike the desperate hopefuls Cowell toys with on TV, these men have given something up to be here, and know it. Every note is compromised. But within Il Divo's weird musical shackles, they give everything they can.
As with every X Factor episode, pop is at its most profound and tackily obvious here: Abba's "The Winner Takes It All", Queen's "Bohemian Rhapsody", Harry Nilsson's "Without You", Sondheim and Bernstein's "Somewhere". Il Divo fling their arms back and throw their voices at them. Kylie veteran William Baker has designed the show with Vegas panache – amusing enough, when infinite ice-blondes in white dresses sway on white pianos for "Nights in White Satin". The orchestra's crude whomping drums remind you this is showbiz. Il Divo's voices buzz around, trying to find a way to hit home.
The set list shadows, surely deliberately, songs selected by Elvis in his Vegas years. During "Bridge Over Troubled Water", as Il Divo's massed vocal and orchestral artillery assault the thunderous climax, they are almost moving. They sing "My Way" – when that's the last path they've taken – and shake hands and offer roses during the humbly beautiful verses of "Amazing Grace".
The contrast with great pop singing is clear. Elvis sang as if his life depended on it, and doing so might save someone else's. Cheap music is only potent if the singer believes in it completely. Pavorotti's version of "Nessun Dorma" was embraced by football and the charts for the same reason. Il Divo are gracious and committed to their audience, but sound like a failed genetic experiment. Emotion never arrives.