There’s never a dull moment when Yo-Yo Ma is on stage.

Working with the world-renowned cellist is almost an improvisational experience, says Colorado Symphony’s Music Director Peter Oundjian.

As one might expect, Ma doesn’t require much prep time; he needs only one rehearsal with the symphony for its Friday night show at Ford Amphitheater, which concludes with Ma’s performance of Antonín Leopold Dvořák’s Cello Concerto in B minor, Op. 104, one of the greatest pieces of music ever written, Oundjian says.

“It’s spontaneous. We don’t expect the same thing with every phrase every time we play it,” Oundjian said. “It’s getting a feeling in the rehearsal for where we might go with the performance. We’re not improvising with notes or time. Where we stretch or what kind of magic moment we’re going to make is in the moment, which is part of why it’s so exciting to be on stage with him.”

Oundjian and Ma are no strangers. They first met 45 years ago as fellow musicians in the Tokyo String Quartet, where Oundjian was first violinist, and have played together many times since.

He compares conducting Ma to a game of tennis against a strong opponent who has amazing shots and an inspirational game, and brings out the best in you. It’s also like being a co-driver in a race car, he says, because you must be ready for anything.

“I enjoy it immensely,” Oundjian said. “He knows, now that we’ve worked together so much, that he can be very free. You can imagine how many times he’s played the concerto. That’s very important that he can be spontaneous, almost as if every time we start the piece, it’s the world premiere.”

As for those magic moments, none of the musicians on stage know what they’ll be or when they’ll come. It’s often when the music becomes internal, Oundjian says, and sometimes arrives as a huge climax. But one thing is true – they take your breath away.

Ma can hold an audience’s attention, no matter what size it is, from an intimate gathering to one with thousands of people. He performs as though they’re all in his living room, Oundjian says.

“Even in a huge place, people experience something personal, which is exceptional. Although he’s individualistic and charismatic, it’s the music first. It’s his belief in the power of whatever piece he’s playing.”

The repertoire

To honor our country’s 250th anniversary, Oundjian created an all-American program, noting that though Dvořák was a Czech composer, he wrote his Cello Concerto in B minor, among other pieces, while staying on 17th Street in New York City.

– “Short Ride in a Fast Machine,” by John Adams: “Adams is one of the great American composers alive today. The piece is a short ride – four minutes of hyper drama, incredible rhythms, and it’s thrilling. It’s a great way to open a concert.”

– “Poem for Orchestra,” by William Grant Still: “Written in 1944, it’s 10 minutes long, but the opposite of Adams. It’s expansive. It has intensity in that it opens up to beautiful melodies. It’s paying tribute to the American jazz idiom. Jazz and blues are so important to America – they’re truly American.”

– “An American in Paris,” by George Gershwin: “The Gershwin pays tribute to that jazz idiom in a beautiful way.”

– Cello Concerto in B minor, Op. 104 (with Yo‑Yo Ma), by Antonín Leopold Dvořák: The Dvořák is 37 to 40 minutes. It depends on Yo-Yo’s mood and my mood. The last movement is very exciting, but at the end, it becomes some of the most expressive music ever written. It’s yearning and tragic. He added that toward the end of the composition, because his sister-in-law had died and he was very fond of her. The ending of the piece is surprising. It ends dramatically. The last five minutes become intense and introspective, and there are lots of magic moments.”

If you go

What: Yo-Yo Ma with the Colorado Symphony and music director Peter Oundjian

When: 7:30 p.m. Friday

Where: Ford Amphitheater, 85 Spectrum Loop

Price: $49-$284; fordamphitheater.live, axs.com