As backup singers for artists like Alicia Keys, Emeli Sande and Estelle, married couple Whitney and Raii Smith already know how to rock a stage. But they had yet to earn their own moment in the spotlight — that is, until Tuesday night's America's Got Talent.

The couple, who met through a gospel group at the University of Illinois, introduced themselves to the judges as the Smiths and sang a rendition of Marvin Gaye and Tammi Terrell's classic duet, "You're All I Need to Get By." 

Source: YouTube
Source: YouTube

They started off slow, gradually building their harmonies until they hit the song's huge declaration of love in the last chorus to floor the judges. 

Source: YouTube
Source: YouTube

Even the brutal Simon Cowell was impressed.

"You started quite normally and I'm thinking, 'This is a little bit karaoke,'" he said. "And then in the middle you both let it rip, and that's when I thought, 'My God, you two can really, really sing.'"

Watch their duet in full below.

Source: YouTube

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