“Nyx,” a 17-minute work by the Finnish conductor and composer Esa-Pekka Salonen, arrives with its own mystique. Did Salonen title his composition after the ethereal figure Nyx, the goddess of the night in Greek mythology and a figure previously best captured on canvas by painters in search of a muse? Salonen himself isn’t saying, but Anna Frankenberg, a representative for the composer, says “he is hard at work completing his description of the piece.”

All shall be revealed Thursday and Saturday evenings, Oct. 27 and 29, when Robert Spano and the Atlanta Symphony Orchestra give the U.S. premiere of “Nyx” — plus Scriabin’s Poem of Ecstasy and Rachmaninov’s The Bells.

Then it’s on to Carnegie Hall for the New York premiere of “Nyx,” and the Orchestra’s first performance at Carnegie without the Chorus since 1997, on Nov. 5. Instead of The Bells, pianist Garrick Ohlsson will perform the Rachmaninov Third Piano Concerto. (He plays the work on the new ASO Media recording, also featuring the composer’s Symphonic Dances, to be released in early November.)

The piece, a co-commission by Radio France, Carnegie Hall, the Atlanta Symphony Orchestra, the Barbican Centre and the Finnish Radio Symphony Orchestra, had its world premiere Feb. 19, 2011, during the final concert of Festival Présences Paris. “Nyx” affords audiences here and at Carnegie a glimpse of kindred sprits at work: Spano and Salonen, luminaries of contemporary music who believe making new music begins at home.

One of the hallmarks of Spano’s career has been an unwavering advocacy of modern composers. Prior to his appointment as the Orchestra’s music director in 2001, Spano was at the Brooklyn Philharmonic where he brought a vital edge to the orchestra’s repertoire and an enthusiastic audience that came from every borough in New York City to hear what some called “classical music’s new era.”

Spano redoubled his commitment when he moved to Atlanta — where he now lives year-round — and founded the justly acclaimed Atlanta School of Composers. Members include Jennifer Higdon, Christopher Theofanidis, Osvaldo Golijov, Michael Gandolfi and Adam Schoenberg, with more composers on the horizon. Their orchestral and choral works are an essential part of the Orchestra’s recorded oeuvre.

“Spano has found that audiences react to these composers with pleasure,” wrote Los Angeles Times critic Mark Swed in 2008. “The Orchestra takes pride in sending its listeners home happy, having been given a big sonic hug.”

Spano and Salonen are not the first conductors, of course, to try and solve the ultimate mystery of the orchestra business, which is how to attract new listeners without alienating established ones. Their reputations for bold choices, however, draw music lovers, and the kind of media swirl that Salonen for one can live without.

“Being a conductor myself, I do have some knowledge of the ‘empty hype’ that goes with this profession,” he said in an interview several years ago with Alex Ross of The New Yorker. “Conductors should be what they used to be — spokespeople for music in their hometown. But [as a composer] only I can write my own music. There’s no one else who can do it for me.”

Having studied horn, composing and conducting at the Sibelius Academy in Helsinki during the 1970s, Salonen initially considered himself to be a conducting composer, until 1983, when he pinch-hit on short notice for a performance of Mahler’s Third Symphony with the Philharmonia Orchestra in London and became a composing conductor virtually overnight. His orchestral works are regularly performed and broadcast around the world.

The Salonen-Spano pairing has prompted a palpable buzz in Atlanta music circles. After all, Spano and the ASO have performed nearly 100 contemporary pieces (works composed since 1950), since 2001, including seven ASO-commissioned world premieres, two additional world premieres, and two U.S. premieres as of the 2011-12 season. The Orchestra has received a total of eight Grammy awards for five recordings of contemporary works and, in 2007, was awarded ASCAP’s most prestigious honor, the John S. Edwards Award for Strongest Commitment to New American Music.

Next up, “Nyx.”

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Tickets and more information on the performance and the complete 2011-12 season are available at aso.org, at the Woodruff Arts Center box office or by calling 404.733.5000.