Tom Sandoval knows reality TV. Vanderpump Rules, The Traitors, Special Forces: World's Toughest Test, The Masked Singer — he's done them all and more. His latest is America's Got Talent, on which he and his cover band, Tom Sandoval and the Most Extras, performed Tuesday, the first semifinal episode of the NBC competition this series.

After hitting his red buzzer halfway through the performance, Cowell told Sandoval, “It didn’t sound great… It might just be me, from where I sat, but that did not sound good, I’m afraid. It didn’t.”...