Garden City’s Ava Nat will advance to the Knockout Round on the NBC singing competition “The Voice” thanks to a save from her coach, Niall Horan.

On Monday’s Night 3 of the Battle Rounds, Nat, 18, was pitted against her teammate Aiden Ross, 20, in a duet on the wistful and remorseful ballad “What a Time,” recorded by Horan himself in a duet with Julia Michaels for her 2019 EP “Inner Monologue Part I.”

“That was just beautiful,” former One Direction singer Horan told the two contenders. “It was everything I wanted it to be and 20 times more. The thing that was making me think who would win this battle would be who can get the emotion across. And that’s why I picked this song,” he explained. “And you guys just sounded so good together.” Calling it “such a hard decision,” Horan chose to retain Ross, citing the Texas A&M sophomore’s consistency.

Nat — née Ava Natalie Milone, a 2024 Garden City High School graduate who is a freshman at Nashville’s Belmont University — thanked Horan “for trusting me with your own song,” adding, “I’ve learned so much from everybody in this process, so I’m really grateful.” Horan then slammed the save button, followed by fellow coach Snoop Dogg doing so.

“There was a split second after [Ross] got picked where I’m, like, ‘Dang, if they don’t use a steal or a save, it is the end of the road,’” Nat told Newsday Tuesday morning. Then, after seeing the redemptive reactions from Horan and hip-hop icon Snoop Dogg, and choosing to remain on Horan’s team, “I actually had this catharsis moment,” she said. “I got offstage and just started crying — just sobbing backstage because it was very overwhelming.”

Snoop Dogg, along with Horan and country-music legend Reba McEntire, had vied to place Nat on their teams after her Blind Auditions performance of Gracie Abrams’ “I Love You, I’m Sorry.” “I felt bad turning down Snoop again,” Nat said, “but I was really grateful that he knew Niall had saved me but he still decided to hit the steal button.”

The episode then shows Nat offstage, telling someone, presumably Horan, that she is not going to let him down — but then Horan comes up behind her, surprising her. Who was she talking to? “So they said, ‘What would you say to Niall?’ And I said, ‘I’m not going to let you down Niall.’ Then he popped up behind me and said, ‘Well, you can tell me right now!’ I was, like, freaking out!” she recalled happily. “I think I said to him, ‘Aren’t you supposed to be in the chair?’ “

Nat’s performance was all the more impressive through her seamless stagecraft in handling a technical malfunction during the duet — rendering it virtually unnoticed.

“The mic[rophone] pack that I was wearing wasn’t attached to my dress,” she said of the tiny electronic amplifier generally clipped onto wardrobe. “It was attached to my skin for this performance — and it actually fell! So you can see me put my hand by on my back — I think it’s right when I walk behind Aiden. And that’s when my stomach dropped on stage!”

Regardless, she got through it without a hitch. Afterward, “I told Niall and he was, like, ‘That was so professional!’ “

Nat has a showcase Wednesday night at a Nashville club with 12 other “Voice” singers from this season. Might she perform a gig on Long Island while at home during the upcoming holidays? Possibly, she said. “You can submit gigs [to the “Voice” producers] for approval. I’m hoping opportunities come up — maybe Christmas caroling or a little showcase maybe in my town. That would be really nice.”

In the meantime, “I’m so happy to be representing Long Island, and I’m hoping that I’m making you all proud. Long Islanders know how to be big fans and they know how to be loud.” And with home-audience voting a component of who stays and who goes, “I really need the fans to rally!”

The Knockouts begin Oct. 27.