During his long career — which started in the 1920s and stretched into the 1980s — choreographer George Balanchine introduced his audience to dozens of composers.

He revered three above all others. But while Balanchine dug deep into the canons of both Tchaikovsky and Stravinsky to create a long list of masterpieces, he rarely turned to Mozart.

But when he did? Magic.

Minnesotans can see the results, firsthand, this Thursday when Pittsburgh Ballet Theatre presents Balanchine’s “Divertimento No. 15” at Northrop auditorium. It’s part of an all-Mozart program that also includes two by choreographer Jirí Kylián: “Petite Mort,” a kind of battle of the sexes that calls upon the adagio movements from a pair of piano concertos, and “Sechs Tänze,” a comedic romp set to “Six German Dances.”

Mozart’s half of the evening will be performed by the St. Paul Chamber Orchestra.

“It’s such an honor for us to work with such a great dance company,” said Kyu-Young Kim, the SPCO’s artistic director and principal violinist. “The combination of live music and ballet is something special, and it’s not something that happens often here. And the St. Paul Chamber Orchestra playing Mozart is a perfect combination. We’re really excited.”

Vaunted history

Russian-born Balanchine was introduced to Mozart’s “Divertimento No. 15 in B-flat Major” at a 1951 dinner party in New York City, where the host played a Toscanini recording.

“And Balanchine fell in love with the music at once and forever,” wrote Richard Buckle in 1988’s “George Balanchine: Ballet Master” (Random House). “Balanchine appeared to have worked with Mozart, as with other dead composers, like a twin who could read his brother’s thoughts.”

The next year, the choreographer used most of the score to create “Caracole” for his New York City Ballet. Four years later, he took the same music — and even some of the same steps — and made the delicate, aristocratic “Divertimento No. 15.”

“It is so close to the music that the chances are no company short of a band of dancing Mozarts will ever be able to attain either the perfection of Mozart or the ingenuity of Balanchine,” wrote Louis Biancolli, music critic of the New York World-Telegram and Sun, shortly after the ballet’s 1956 premiere.

Today, “Divertimento No. 15” continues to radiate a freshness that suggests it debuted yesterday, not 62 years ago. That’s Balanchine.

“I love it all,” said Terrence Orr, Pittsburgh Ballet Theatre’s artistic director. “I love the opening, where everyone comes on and gets introduced. And the finale blows you away. Suddenly, it’s over. It’s 32 minutes, and it feels like it’s 18. That’s a nice feeling.”

Structurally, the ballet follows an unusual format. Rather than utilizing an even number of couples, Balanchine divvied up the principal roles into five women and three men, their odd-numbered mathematics framed by an ensemble of eight women.

“It’s difficult, putting five and three together, and making those numbers into equal geometric formations, but Mr. B didn’t worry about it,” said Orr. “Even though there’s not perfect symmetry, it shows very much in this ballet. That’s part of his genius.”

A theme-and-variations section boasts a series of six dizzyingly demanding solos, an ever-escalating exercise in neoclassical speed, clarity and musicality. The ballet’s high point is the adagio, where five duets — courtly, romantic, occasionally pensive — flow naturally, one after the next.

“With all of his ballets, Mr. Balanchine is extremely musical, he was almost a musician first,” said Orr. “He magnifies the sound of the music, and brings it alive.”

‘Music as entertainment’

The format of the divertimento (from “divertire,” the Italian word for “to amuse”), popular in the 18th century, was fairly unstructured, with no set rules regarding length or number of instruments.

“The divertimento stems from this idea of music as entertainment,” said Kim. “It’s meant for the outdoors, for party music. Not that it’s not meant to be listened to, but it’s not the sole focus of attention. It’s a diversion, something to take your mind off the troubles of the world. That’s partly why it works so well for the ballet, because it’s so light, and fun, and full of character.”

In 1777, in honor of a family friend, Mozart wrote his 15th divertimento (five more were to follow before his death in 1791), dividing the composition into six movements.

Balanchine, glossing over his usual fidelity to composers’ intent, skipped a few of the score’s segments. In the late 1960s, the choreographer, forever tinkering with his ballets, inserted a brief cadenza into the andante. The Mozartian music was created by the late John Colman, a Duluth native famous in New York dance circles as a skilled piano accompanist.

Mozart’s original score is written for five strings — two violins, viola, cello and double bass — and two horns.

But when the SPCO takes command of Northrop’s orchestra pit, the ensemble’s full complement of string players will be on hand.

“You need that cushion of sound, because the audience’s attention is on the dancers,” said Kim. “It’s a very different experience, playing for the ballet.”

The SPCO’s current season is dotted with Mozart. In this array of symphonies, concertos and quintets, “Divertimento No. 15” stands out.

“It’s a very difficult score, which is partly why it’s not done all that often,” said Kim. “It’s delicate and precise, and that’s very similar to the way that the dancers have to nail their movement. The filigree of the dance has to be perfection, so there is that parallel, because that’s what’s demanded of the musicians.”

In the decades following its premiere, the ballet (which quickly grew into an audience — and dancers’ — favorite) has occupied a cherished place in New York City Ballet’s vast repertoire.

Balanchine died on the last Saturday of April 1983, at Roosevelt Hospital in Manhattan. New York City Ballet was performing down the street at its Lincoln Center home. And before the matinee performance, company co-founder Lincoln Kirstein stepped before the curtain to say: “I don’t have to tell you that Mr. B is with Mozart and Tchaikovsky and Stravinsky.”

On the program that evening? “Divertimento No. 15.”