When conductor Leonard Slatkin was recently researching the upcoming concert seasons of the 15 largest-budget U.S. orchestras, he made a startling discovery. While key living American composers are mostly well-represented, their 20th-century predecessors are all but ignored.

So, other than Samuel Barber’s increasingly popular Violin Concerto and a smattering of selections by such well-known names as Charles Ives, George Gershwin and Leonard Bernstein, works by many other notable 20th-century composers such as David Diamond, Roy Harris, Roger Sessions, Walter Piston and William Schuman (below right) are nowhere to be found.

“What surprised me,” Slatkin said, “is how literally no orchestra pays attention now to the composers who shaped so much of the symphonic landscape of the country. It’s just amazing to me that no one today is looking at this repertoire at all – either the young or old conductors. They just don’t do it. And it makes me wonder: Are we completely losing touch with this aspect of the culture?”

Slatkin, music director of the Detroit Symphony and France’s Orchestre National de Lyon, spotlighted this historical slight in March on huffingtonpost.com in a blunt essay titled, “Where Did Our Musical Legacy Go?” The piece provides an ideal backdrop for Slatkin’s return April 17-22 to the Chicago Symphony Orchestra, where he will conduct exactly the disappearing repertoire he describes.

The program will include Barber’s infrequently heard Overture to “The School for Scandal” (1931) as well as the CSO’s first-ever performances of Schuman’s dark Symphony No. 6 – 66 years after its world premiere.

schumanIn addition to serving as president of the Juilliard School and the first president of Lincoln Center, Schuman (1910-1992) left a wide-ranging compositional legacy that includes eight symphonies (he withdrew his first two). But even professional musicians are unfamiliar with most of his work, Slatkin said, and today’s music students have no idea who he is.

Because Schuman is so little known, Slatkin plans to present a four- to five-minute talk on the composer’s distinctive musical language before the CSO’s performances of the Sixth Symphony.

“I’ve always loved the music,” Slatkin said. “I think it is so unique. Three bars into any Bill Schuman piece, and you know it’s him. Nobody else could write that way. I thought it would be nice to show the audience what makes him special, why this is a unique voice – not just another American composer who wrote symphonies.”

Rounding out the program is the local premiere of Mead co-composer-in-residence Mason Bates’ Violin Concerto, which Slatkin recently recorded in London with guest soloist Anne Akiko Meyers, and Gershwin’s ever-popular “An American in Paris.” “You need ‘American in Paris’ to sell the program, but it works,” the conductor said. “It fits in nicely with the Bates. Both are jazz-infused.”

During much of the 1969-1991 tenure of the CSO’s music director Georg Solti, Slatkin was a frequent guest conductor, along with Claudio Abbado and Erich Leinsdorf, sometimes leading three to four weeks of concerts a season. “We were called the Gang of Four,” Slatkin said.

But he has not appeared on the Orchestra Hall podium since 2011, and he wanted to make this visit special. Since his debut program in 1974 with the CSO included Piston’s Symphony No. 2 and similar repertoire has been part of many of his subsequent engagements, an all-American lineup seemed the way to do it.

“I’m turning 70 this year,” Slatkin said, “and I thought, in some of the places I go, I want to do things that have helped me shape a career.”

The decline of historical American repertoire on orchestral programs hits Slatkin especially hard, because he made his name in part by focusing on just such works as an up-and-coming conductor and later as music director of the St. Louis and National symphonies. “There are really not many of us alive anymore,” he said, “who knew these composers and had that direct contact, and when we’re gone, what will happen to that tradition? It seems to me that it will completely disappear, and that’s a tragedy if that happens.”

One solution to this potential loss of a major facet of the American musical legacy lies with today’s young American conductors. Just as he carved out a niche in this repertoire, so could some of his potential successors. “Do we need another person out there doing a Mahler cycle?” Slatkin said. “We’re glad to have them. It’s all fine, but it’s harder and harder now to make a real mark now, and you need some degree of specialty.”

Meanwhile, Slatkin plans do all he can to keep shining the spotlight on America’s forgotten symphonic music both by programming it, as he is doing during his guest engagement with the CSO, and writing about it.

More from Leonard Slatkin on leading two orchestras and other subjects:

Serving as music director of the Orchestre National de Lyon: “The repertoire is certainly different. In France, we’re called a national orchestra. Fortunately, I have a good background in French music. My main conducting teacher was French – Jean Morel. We’re not just only playing Berlioz, Ravel, Debussy and things like that, but we’re also doing [Gabriel] Pierné, [Henri] Rabaud and [Jean] Roger-Ducasse, some of the composers who have also gone by wayside for the French. They are not even done in Paris, so we do them, and we’re enjoying discovering all this repertoire. It is a lot of fun.”

Splitting his time as music director between French and American orchestras: “Within the standard repertoire, I’m doing many pieces in both places, because I learn from each place, and I can bring some of the styles and qualities that we have in Lyon to my orchestra here in Detroit. This orchestra has a long background with [1951-1962 music director] Paul Paray in the French repertoire. Not that many people are left from that time, but there’s a kind of sound that they have that is nice and interesting in that sense. And in Lyon, I’m trying to bring them a kind of American sense of virtuosity to the playing. I’m really enjoying this.”

Limiting his guest conducting: “This coming summer is going to be my last summer of guest conducting altogether. I’m going to take some time. I have two more books I want to write. I’m writing music. I want to travel. It’s time to enjoy myself.”

Kyle MacMillan, former classical music critic of the Denver Post, is a locally based freelance writer.

VIDEO: The Theodore Pressler Co. presents a video portrait of William Schuman, via YouTube: