It has never seemed so obvious that Napa County is overflowing with talented musical youth as on Saturday night, when 13 aspiring pop stars took their turns on the Napa Valley Opera House stage in the last preliminary round of the Idol NV teen singing contest.

With the acclaimed Napa High School production of “The Music Man” in its final performance at the same time, you might have expected all that school’s top singers to be on-stage at the District Auditorium. But you’d be wrong: Napa High’s Chelsea Brock snared one of the two remaining spots in the Idol NV final round March 17, with her sassy and note-perfect rendering of “At Last.”

Brock had initially performed the Mack Gordon-Harry Warren ballad in round four of the competition on Feb. 24; that night’s judges gave her high marks, but ultimately chose two young men as finalists. Saturday’s panel of judges — businessman and musician Steve Carlin, winery executive and soprano Deborah Tonella and composer Thomas Schoenberger — were bowled over by Brock’s reprise.

“You remind me of a cat,” Tonella told the 17-year-old, praising a dynamic voice that ranged from kitten-tender to lioness-bold as Brock prowled the stage, casting melting glances that added some heat to the song’s romantic lyrics.

The evening’s second finalist in the ultimate battle for the Idol NV crown also chose a beloved American ballad, but to very different effect. In her first appearance on the Opera House stage, 15-year-old Devon Hadsell struck a classical note with upswept hair and a full-length gown, standing serenely before the microphone as she sang the Gershwin brothers’ yearning “Someone to Watch Over Me.”

Hadsell’s pure tone, elegant presentation and sweetly romantic delivery left  judges and audience smitten: At the end of the night, ticketholders voted the Vintage High School student one of their two top choices, earning her an extra prize along with the last remaining slot in the March 17 final round.

Audience members also gave their hearts to Emily Duncan of Silverado Middle School, the evening’s youngest contestant, who recently turned 13. Pretty in pink and pearls, with a voice already blooming into richness, Duncan romped through Rodgers and Hart’s lively show tune “You Took Advantage of Me.”

“You were a real star — you had that rhythm down, you knew what this piece was about,” said Tonella, adding “You were darling.”

Coincidentally, the evening’s three winners — finalists Brock and Hadsell and audience favorite Duncan — all chose vintage songs from what judge Schoenberger called “the American songbook.”   

Most of Saturday’s repertoire reflected more-current tastes in show tunes, but Stephanie Sasloff stood out with her selection of the 1969 Golden Globe-nominated ballad “What Are You Doing the Rest Of Your Life?” by Michel Legrand, Alan Bergman and Marilyn Bergman.

From her first smoky note, the 17-year-old from Vintage High drew her listeners into the Bergmans’ intimate lyrics, transforming the Opera House into a hushed cabaret. Though she won’t be going on to the Idol NV finals, Sasloff has at least one more opera house appearance ahead of her — on the famed stage in Sydney, Australia, this summer, as part of the People to People student-ambassador program.

Both Alexandria Cero and Shaina Hill sang the inspiring “Only Hope,” written by Jonathan Foreman for the 2002 Mandy Moore film “A Walk to Remember.” (A third contestant who had also planned to sing the song hastily changed her choice before show time.)

Cero, a 16-year-old from Vintage High who drew the evening’s opening slot, overcame some initial nervousness to win encouraging comments from the judges panel. “You really seemed to believe in your lyrics,” Tonella said, while Schoenberger praised Cero’s “tempi” and Carlin her stage presence.

Schoenberger called Hill, a 14-year-old Napan attending River School, “a natural balladeer” for her performance of the same song later in the evening; Tonella complimented Hill on her breath control.

Olivia Hurst of American Canyon made the wise choice to substitute another song for the Foreman number, earning wild applause and the judges’ admiration for her performance of “I Have Nothing,” originally a Whitney Houston hit from the 1992 film “The Bodyguard.”

“You sound like a pro,” said Tonella — perceptively: Just last month, the home-schooled 16-year-old made it to the “final 40” in auditions for the mega-hit American Idol TV show.

The Disney film “Anastasia” gave 17-year-old Ashley Antovich her song, “At the Beginning,” by Donna Lewis and Richard Marx.

“Great performers make people feel good, and you certainly did that tonight,” Carlin told the Vintage High senior amid cheers from the crowd.

The Vintage-heavy audience also raved for 15-year-old schoolmate Michelle Tubman, who sang the demanding aria “Think of Me” from Andrew Lloyd Webber’s “Phantom of the Opera.”

 “I was very impressed with your exacting pitch and your good breath control,” Tonella said.

Some of the evening’s loudest cheers rang out for 17-year-old Vintage High student Gerrell Roberts, Saturday’s only male vocalist — and the only contestant in the Idol NV series to make singing Stevie Wonder seem effortless. Fans and friends clapped along, then roared with approval after he sang “I Just Called To Say I Love You” (another movie hit, from 1984’s “The Woman In Red”).

“I don’t think they liked it that much,” joked Carlin.

Roberts’ smoothly soulful performance was followed by a real surprise: 16-year-old Kerstin Holzer of Napa, who rocked the Opera House with a big voice and some killer stage moves to the 1976 Queen hit “Somebody To Love.”

No evening gown for this New Tech High student, who swaggered in jeans and tossed her leather jacket aside as her voice soared through Freddie Mercury’s glam aria.

“You’ve got a playful stage presence,” said Schoenberger, adding “You also have something that’s very rare, which is charisma. You usually don’t see it in someone so young.” Tonella complimented Holzer’s dynamic range and vocal control, and called her “gorgeous on stage.”

Further evidence that Napa High has vocal talent to spare, 18-year-old Althea Kent sang “Angel” by Canadian singer-songwriter Sarah McLachlan.

“You have a very rich voice; I closed my eyes and it sounded like a recording,” Carlin told Kent, whose mother had dragooned her into entering the contest.

“I’m glad you were convinced … this was a wonderful opportunity to hear you,” Tonella said. “I hope this encourages you to continue performing.”

Classmate Melissa Loper, who sang a Mariah Carey ballad in round four of the competition, returned with the lively country-rocker “I Wanna Do It All,” a hit for Canadian singer Terri Clark. Loper — whose fans may be among the most fervent cheering sections the Opera House has ever seen — pleased the judges with her confident performance and her stylish country outfit: “May I borrow those boots?” Tonella asked jokingly.

Nearly 300 ticketholders turned out for Saturday’s last qualifying round of the contest, and the March 17 final is likely to be packed. That’s when the 10 top judges’ picks from the five rounds to date — eight young women and two young men — will have one more chance to sing for the title of Idol NV and prizes, including laptops and scholarships, donated by local businesses. For more information, call 226-7372, or visit www.nvoh.org.