Aaron Copland is certainly not considered a "band composer" by any stretch of the imagination, but he certainly contributed quite a piece to the wind repertoire. Emblems is generally regarded Copland's only piece written for band, as the result of Keith Wilson and the CBDNA in 1964. However, Copland did notably compose two other pieces for winds alone (Fanfare for the Common Man and Ceremonial Fanfare) as well as arrange many of his own pieces for concert band (Outdoor Overture, Lincoln Portrait, Preamble for a Solemn Occasion, Variations on a Shaker Melody, and Suite from the Red Pony). Other arrangers have also worked out some other pieces for band as well.
An NPR piece on the Copland Centennial describes Emblems as such: This "11-minute, one-movement work is a sampler of Copland's varied output: simple triadic passages, polytonality, folk melodies, dissonance, waltzes, polymeters, and elements of jazz all appear. The work's initial reception was lukewarm, in part due to its technical challenges, but as Copland's only work for band it won a secure place in the repertoire. Of the work's cryptic title, Copland said only that it was meant 'to suggest musical states of being ... the exact nature of which must be determined by the listener.'"
As part of the NPR article, you can download the Coast Guard Band's Copland concert that was broadcast on NPR. That link is available here and the full NPR article can be accessed here.
The notes below are from the U.S. Army Field Band's recording of Copland's music entitled "The Legacy of Aaron Copland" and the full notes can be accessed here. This recording is an excellent Copland resource for anyone interested in the wind music of Aaron Copland.
Aaron Copland, Emblems
United States Army Field Band, Finley R. Hamilton, conductor
For a number of years, conductors of high school and university symphonic bands had hoped that America’s most revered composer would write an original work for them. In the summer of 1964, Copland began work on a commission from Keith Wilson, president of the College Band Directors National Association (CBDNA). Wilson’s intent was for Copland to add to the repertoire an original piece for band that would be “representative of the composer’s best work, and not one written with all sorts of technical or practical limitations.” The result of this commission, Emblems, is a single-movement, eleven minute work in ternary form. The entire composition is unified through the use of a harmonic germ, which in certain sections unfolds similar to an extended chaconne. Despite its polytonal character, Emblems uses fewer harmonic complexities and significantly less dissonance than Copland’s previous two works, the twelve-tone Connotations (1962) for orchestra and Nonet (1960) for strings.
According to Copland, embedded in the quiet, slow music the listener may hear a brief quotation of a well known hymn tune, Amazing Grace, published by William Walker in The Southern Harmony in 1835. Curiously enough, the accompanying harmonies had been conceived first, without reference to any tune. It was only a chance perusal of a recent anthology of old ‘Music in America’ that made me realize a connection existed between my harmonies and the old hymn tune.”
Regarding the title, Copland writes: “An emblem stands for something— it is a symbol. I called the work Emblems because it seemed to me to suggest musical states of being: noble or aspirational feelings, playful or spirited feelings. The exact nature of the emblematic sounds must be determined for himself by each listener.”
Emblems was premiered at the CBDNA National Convention in Tempe, Arizona, on December 18, 1964, by the Trojan Band of the University of Southern California, conducted by William Schaefer. As Copland’s only original work for band, Emblems has firmly established itself in the twentieth century wind band repertoire.