Symphony Hall rehearsals don’t usually include a laying on of hands, but that’s what happened when conductor Thomas Wilkins waded into the orchestra to save the opening bars of Edvard Grieg’s “Peer Gynt.”
“Everyone here is on your side,” the conductor said, calmly placing his palms on the heads of two flutists who’d tackled the bucolic passage. “You have to say to [the audience]: There are these things called trees, and cows, and stuff. It’s unlike anything you’ve ever seen, but your soul will recognize it.”

Wilkins’s method at the Wednesday night rehearsal may have been unorthodox, but so was his orchestra: 100 or so eager amateur musicians from around Massachusetts, chosen by lottery to take part in “Onstage at Symphony.” The four-day program culminates with a free performance this Saturday at Symphony Hall.
“It’s like playing a softball game at Fenway Park,” said Elliot Pittel, a child psychiatrist and trumpeter from Newton. “Being exposed to how the Boston Symphony Orchestra plays and getting a little glimpse of how things work — it’s like fantasy camp for musicians.”

Ages 21 to 76, the players range widely in technique, talent, and experience. Some, like Somerville violin teacher Masami Rodriguez, are conservatory-trained musicians who have played since childhood, while others, such as Pittel, took decades off from their instrument to pursue a career. They’ve never played together before. But they’re all in the same boat: After three rehearsals, they’re on. No pressure.

Or at least not for Wilkins, who launched the program in 2015 and uses humor, respect, and a little tough love to shape their raw potential into a coherent musical whole.