Diana DeGarmo and Ace Young
05/24/2012 at 01:00 PM EDT
It was the engagement
seen 'round the world Wednesday night on American Idol
, so how did Ace Young manage to pull off his surprise proposal to fiancée Diana DeGarmo?
With a little help from his Idol
family, it turns out.
"I called [producer] Nigel [Lythgoe] directly last week and said, 'I want to do this. I'm going to do this. Is there any way I could do it at the show?' " Young, 31, told PEOPLE at the Ford-sponsored American Idol
season 11 finale post party. "He said 'Yes, I'm not going to tell anybody until the day of ... [and] I want you to figure it out with Ryan [Seacrest]
But DeGarmo, 24, who was "completely caught off guard," almost thwarted Young's big plan at the last minute.
"I actually almost got up to go to the bathroom to fix my hair," she said, laughing. "And then I just started shaking [on stage]."
As his fiancée showed off her new sparkler
at the party, Young explained what went into the making of the ring.
"A month ago, she said, 'Gold needs to come back,'" the season 5 finalist said. "I was like, I agree, so mental note. Her favorite thing is a sunflower and she loves yellow, so one of our dear friends [helped me] put together a ring that has a yellow diamond, a gold band and two smaller diamonds on the side that are clear, so it's like a sunflower."
And though the newly engaged couple – who recorded a duet on DeGarmo's recently released EP Live To Love
– have yet to start planning for the big day, one thing's for certain – there will be "plenty of music" at their wedding.