It is the time everyone has been waiting for: The live shows are here!

Tuesday's episode of "America's Got Talent" kicked off the first quarterfinal round, broadcasting live from Hollywood's Dolby Theatre. That means anything can happen.

Only seven of the 12 acts will advance to September's semifinals, adding more pressure for the remaining contestants to wow America. And the competition is stiff. Tuesday's field included three Golden Buzzer winners – Kodi Lee, Sophie Pecora and Luke Islam – and wildcard Ansley Burns, who returned after her tearful elimination in the Judge Cuts.

Living up to the moment, however, wasn't an issue for Lee, who judge Gabrielle Union said "changed the world" with his audition and did the same again Tuesday.

'AGT' goes live:The best acts headed into the final rounds of summer's top show

More:'America's Got Talent': Wildcard Ansley Burns gets standing ovation for her return

Lee, a blind singer with autism, performed a powerful rendition of Simon and Garfunkel's "Bridge Over Troubled Water," showcasing his vocal range and impressive piano skills.

Simon Cowell revealed that Paul Simon specially OK'd Lee to perform the song "because he saw your audition," which has over 42 million YouTube views.

"I want to thank Paul Simon, who never really gives permission for anyone to sing ('Bridge Over Troubled Water') because it's very precious to him, and he gave (Lee) clearance within 30 minutes," Cowell said.

Lee's performance brought tears to Union and Julianne Hough's eyes and prompted the crowd to repeatedly chant "Kodi! Kodi!" among applause.

"Who you are, what you stand for and what you continue to do makes the world become so much of a more beautiful place," Union said to her Golden Buzzer act.

Cowell added: "You are genuinely one of most extraordinary people and talents we’ve had the great fortune to have on any show we’ve ever made. God bless you."

Impressionist Greg Morton also raised the bar with his spot-on voice impressions of films “The Lion King,” “Shrek,” "Ace Ventura: Pet Detective," "Braveheart" and "Guardians of the Galaxy."

"I had a concern, coming to the Dolby, if you would own the stage or not, and you actually proved me completely wrong," Cowell said. "This is such a step up from you previous audition."

Howie Mandel added, "You are the biggest variety show in one man."

Other acts that performed Tuesday included black-light painter Alex Dowis; danger act Bir Khalsa; singer Carmen Carter; the Emerald Belles drill dance team; girl group GFORCE; the acrobatic Messoudi Brothers; and the Voices of Service quartet.

The fate of the contestants is no longer in the judges' hands. It's up to America.

Fans can vote up to 10 times for each act on NBC.com/AGTvote or through the "America's Got Talent" app. The acts advancing to the semifinals will be revealed during Wednesday's results show, which will include guest performances from "AGT" winners Shin Lim and Bianca Ryan. (NBC, 8 EDT/PDT)