With all its brass curves, a lost French horn wound up in what the 1927 Minneapolis Daily Star called “the center of one of the most amazing coincidents …”

Wilhelm Muelbe and Fred Keller were born nearly seven years and 4,300 miles apart in the late-1800s. They wound up fighting — and playing in military bands — on opposite sides of World War I a century ago.

Muelbe, a German musician born in Rostock in 1888, gave up his chair with the famous Grand Opera orchestra in Cologne to fight with the Germans along the Russian and Western fronts from 1914 to 1918. He survived unscathed, although a bullet once pierced his knapsack.

Keller was born in Minneapolis in 1895, the son of a German immigrant father and Wisconsin mother. Census rolls show Fred as a newspaper circulation manager in 1930, a leather salesman in 1940 and an ammunition maker in New Brighton by 1942.

Back in 1918, Keller was a member of the band connected with the Army’s 151st field artillery battery made up largely of Minneapolis men. They went on the offensive near Saint-Mihiel in northeastern France.

During five hellacious days in mid-September, American forces deployed one of their most audacious combat operations, using war planes for the first time and aggressive tank assaults under the command of young Col. George Patton, who would become famous in the next world war. The victory at Saint-Mihiel came at high cost: 7,000 American casualties, but more than 10,000 Germans taken prisoner.

“Coincidences are spiritual puns.” — British writer G.K. Chesterton (1874-1936) “Coincidence is God’s way of remaining anonymous.” — Albert Einstein (1879-1955)

“The first few shells of the great drive came over,” Muelbe later recalled, “and the German army was declared to be in a state of ‘high alarm.’ ”

With the terrain pocked with shell craters, the German retreat was cut off. “Then came the zero hour,” Muelbe said, “and the first waves of American troops moved ahead against the German trenches.”

At that last minute, Muelbe hid his music and instruments in holes dug out of a hillside near the French town of Vandieres.

“I said goodbye to all my solo music, and all the band music,” Muelbe recalled, “and also to my own horn, a Cruspy French horn with a piece of German silver on its side where my hand rested.”

Keller, meanwhile, was part of the mop-up duty that followed and “we found the deep dugouts the Germans had built along the side of the valley,” he said, including the German musical cache.

The Minneapolis conductor of the Army’s 151st band, Michael Jalma, wanted the sheet music. “But we bandsmen were interested in the instruments,” Keller said. Among the spoils collected: two French horns, a trumpet and a Kaiser bass horn.

The war ended a few months later with Germany’s surrender. Muelbe immigrated to America in 1923, joining the Minneapolis Symphony Orchestra. By 1930, Muelbe lived within 6 miles of Keller in Minneapolis.

In 1925, Keller was helping the Minneapolis Symphony prepare for a performance of Tchaikovsky’s 1812 Overture. A first-generation American, he spoke German and started to chat with a symphony librarian and one of the musicians — Muelbe.

Muelbe and Keller quickly realized they had both been at the Battle of Saint-Mihiel. Then Keller mentioned the French horn he kept as a battlefield souvenir.

“Whose horn was it?” Keller asked at a 1927 meeting to which he brought the beat-up instrument.

“Whose horn!” Keller’s enemy-turned-neighbor exclaimed. “Why that’s the horn I played in concert the day before the Americans took our line. It’s my horn.”

So Keller gave back Muelbe’s horn that day, according to Keller’s grandson, Fred R. Keller.

“The two played side by side in the French horn section of the Minneapolis Symphony for several concerts,” the grandson said. The elder Fred went on to lead the Keller Gopher Band, which played all the city parks each summer well into the 1950s.

Keller died in 1959 at 64 and is buried at Crystal Lake Cemetery in north Minneapolis. He and his wife, Marie, had three children. Records show Muelbe played with the Minneapolis Symphony into the 1940s. A 1950 Minneapolis directory shows him in St. Louis Park, working as an instructor for the Minneapolis College of Music. He moved in the 1960s to San Antonio, Texas, where he died in 1966 at 78. He and his wife, Anna, had a daughter.

Keller’s grandson was 12 when Fred died. He retells a story his grandfather often shared about Keller’s troop ship arriving in New York City in 1919 after the war.

While waiting for the train ride home, the 151st Rainbow Division spent the night in Carnegie Hall. As they settled into their seats, a band started playing, stage lights came on and out came the most famous tenor in the world, Enrico Caruso.

“He gave the soldiers an impromptu welcome-home concert and finished up by singing ‘There’s No Place Like Home.’ Grandfather said every soldier in the place was crying.”

Curt Brown’s tales about Minnesota’s history appear each Sunday. Readers can send him ideas and suggestions at mnhistory@startribune.com. His new book looks at 1918 Minnesota, when flu, war and fires converged: https://tinyurl.com/MN1918. Podcasts at www.onminnesotahistory.com.