Their performance capped a demanding three-day "orchestra festival" for the region's Pennsylvania Music Educators Association districts.
Schools sent their best musicians to district orchestras in January; the top performers from those came together Thursday for the regional orchestra.
The students, most of whom had never played together before, spent all day rehearsing Thursday and Friday, with breaks for meals.
"I was exhausted at the end of Thursday," said Anna Thompson, a 17-year-old senior flutist from Phoenixville Area High School.
But it was worth it, Thompson said, for the opportunity to play with high-caliber musicians her age.
"I get to play with an ensemble that I might not be the best at," she said. Thompson, the only student from her school to attend the festival, was principal second flute, the equivalent of third in line.
Soo Han, the guest conductor for the festival, said the orchestra was one of the best he had worked with.
Han, who now teaches in Indiana, grew up in Lancaster County. He jumped at the chance to work with the regional orchestra, he said, because he had long known the region to produce strong musicians.
"It's a huge honor to be asked, and knowing the work that went into it, it's a huge honor," he said. "It's absolutely incredible, the work the students have done . . . this region is just phenomenal."
From the regional orchestra administrators chose standouts to go to join an all-state orchestra.
Before the list was announced, Yeo said it was "still a little nerve-wracking" to not know for sure if she would be selected for the state performance.
She was. So was Thompson.