One by one, the young composers scurried into Osmo Vänskä's office to discuss — in 10 minutes or less — a piece of music they'd written and rewritten over months, maybe years, and were now placing in his hands.

The maestro had done his homework. He had questions.

"The recording that I heard, the first half was much faster," he said to Alyssa Weinberg, noting that she had called for a tempo of 60 beats per minute. "I have my opinion —"

"Yes, it should be slower," she said.

"It's lacking a little bit of singing," Vänskä said. "You're OK if I —"

Weinberg nodded rapidly.

Seven composers in their 20s and 30s arrived in Minneapolis on Sunday for a week of such moments with Vänskä, the Minnesota Orchestra musicians he conducts and ­Pulitzer-Prize winning composer Kevin Puts. The five-day Composer Institute culminates in a Friday night concert, when the newbies will hear their pieces performed by the biggest and best orchestra that's ever played them.

"A lot of them have never heard an orchestra of this level," said Puts, the celebrated composer who's led the institute for five years. It's a little like encountering a new instrument. "Oh, this is what it can sound like if I write this melody," he said. "That will inspire their next piece."

But before that concert, there are workshops and one-on-ones. Advice about publishing and recording. And, before the first rehearsal on Tuesday morning, some shared anxiety.

"When you have 80 people playing something with your name on it, it's nerve-racking," said Viet Cuong, 28, a student at the Curtis Institute of Music in Philadelphia. "It's a mixture of nerves and anxiety — but with excitement, obviously."

Playing for size

Sitting around a table in Orchestra Hall's atrium Monday morning, the composers introduced themselves and listed where they live, the cities hinting at their Princeton and Juilliard pedigrees. A staffer handed out key cards and explained the skyways. Puts pointed out their luck with the mid-30s weather: "That's huge for Minnesota."

Then they went on a tour.

As the composers stepped through the side door and onto the stage, someone flipped on the lights, illuminating the dozens of large white cubes behind them and the hall's more than 2,000 seats in front of them. "This is Orchestra Hall," said Mele Willis, artistic operations manager. "Has anybody ever been here before?"

"It's my first time in Minnesota," said Weinberg, who declared, as a 16-year-old at a music summer camp, that she would become a composer. She went on to study composition at Vanderbilt University, the Manhattan School of Music and the Curtis Institute. Now 30, she's a doctoral fellow at Princeton.

This weeklong program, co-run by the American Composers Forum in St. Paul, is part of a national effort to train a new, more diverse generation of composers. Partly because of its big-time alumni (among them: Missy Mazzoli, class of 2006), it attracts composers from across the country, some with long résumés.

But for even a top young composer, working with a professional symphony orchestra is a rare opportunity.

"No matter what the level or context, finding four people to play a string quartet of yours is way easier, way more financially possible," Weinberg said. "These large existing institutions we don't have the same kind of access to."

They don't often have access to a mentor like Puts, either. Since winning a 2012 Pulitzer Prize for Minnesota Opera's "Silent Night," Puts has been picked for commission after commission, earning raves along the way. These days, he's composing an orchestral song cycle based on the letters of Georgia O'Keeffe and her husband, Alfred Stieglitz, set to tour with superstar soprano Renee Fleming.

Sometimes, Puts weighs whether running the institute is "too much for me," he said. "But whenever I'm here … I'm moved by the whole process."

On Monday afternoon, Puts pulled out his rimless reading glasses and turned the page of Cuong's piece, "Moxie."

"Did you get any issues from the flutists?" Cuong shook his head. "That's good," Puts said.

Puts and Cuong met a decade ago, when Cuong was studying at Peabody Conservatory, where Puts teaches. So during this hourlong session, they talked composing and computer programs, trading tips and jokes.

"Ten years ago, it would have been hard for me to write a piece like this," Cuong said. In a world of sometimes amorphous new music, "Moxie" might have felt too bold, too straightforward, he said.

Few composers stick with a musical idea long enough to develop it with repetition and change, Puts said. But that's not a cop-out or a crutch.

"To me, that's the mark of a good composer," he told Cuong. "Here's an idea, see how far you can go with it."

'OK, it's gonna be good'

On Tuesday morning, after their meetings with Vänskä, the composers filed into Orchestra Hall. The musicians were onstage, warming up, and the hall was filled with warm dissonance. One by one, the composers stood up, beside Vänskä, and introduced their works.

Cuong said a few words about "Moxie." The musicians tapped their feet, an orchestra's version of applause. Then he took a seat in row eight, beside Puts, for the first run-through.

The music launched with a flurry of flutes and percussion. As the drummers gelled, the flutists locked in, layering and building.

Cuong turned to Puts: "OK, it's gonna be good."

During a rehearsal break, he sighed with relief. In working through sections of the piece, Vänskä tweaked the same moments Cuong had filed in his head. "It's amazing when a conductor almost telepathically knows what you're thinking."

With a French horn and a warm grin, Herbert Winslow approached Cuong. The pair shared a few Curtis stories (Winslow graduated from the institute in 1976), then launched into Winslow's concern: a line Cuong had notated with "bells up." Asking the horns to turn their instruments up at that moment is tricky, Winslow said.

"It's high, right?" Cuong said.

"It's not that — it's the time before it," said Winslow, associate principal horn. It takes time to prepare for that move, as well as time to come down from it. Cuong suggested taking out a note. "I would simply mark this up a dynamic," Winslow suggested, making clear that the horns ought to play louder. "If you really want this line brought out — which, it's a very cool line —"

"Let's just make it fortissimo," Cuong said.

He thanked Winslow once, twice. "Literally, for the rest of my life, when I write 'bells up,' I will know they need time to prepare," Cuong said, nodding, smiling. "I'm still learning tons of stuff."

Jenna Ross • 612-673-7168