American Composers Orchestra, at Zankel Hall It has always been the American Composers Orchestra's mandate to explore the full range of American classical music, and in its 35 seasons it has done so without a trace of dogmatic ax grinding. Still, the orchestra has often compartmentalized, devoting a program to one or two approaches, and the next to a couple more. That makes sense. If you try to show everything at once, you may end up with the kind of motley program that George Manahan led on Thursday at Zankel Hall. Gabriel Kahane performing with the American Composers Orchestra. You could not have asked for greater breadth. An angular, efficiently aphoristic vocal setting by Milton Babbitt represented the severe end of the contemporary American spectrum, and a pop-tinged song cycle by Gabriel Kahane was its polar opposite, a sample of the hybrid style currently in vogue. Tuneful, harmonically accessible concertos by Copland and Michael Daugherty held the middle ground. All but the Copland piece were commissioned by the orchestra, which says a lot about the organization's ambition and eclecticism. But all that variety left you feeling that there was not enough of anything in particular. Surely anyone who admired Babbitt's refined, virtuosic approach to line and harmony would have admired the clarity that the soprano Judith Bettina brought to "From the Psalter" (2002) and been disappointed that this score's five densely packed minutes were all that Mr. Manahan and company were offering this time. It was a huge leap from the Babbitt to Mr. Daugherty's "Trail of Tears" (2010), an attractive flute concerto wrapped in a meditation about the forced 800-mile march of 15,000 Cherokee from Tennessee to Oklahoma in 1838 and 1839, during which 4,000 died. You would expect a wrenching, weighty piece, and Mr. Daugherty's score is not without drama or color, captured mostly in the percussion writing that underpins the end of the first movement, "where the wind blew free - ." But dark moments are few, and no amount of program-note-driven self-persuasion can make this piece into something other than it is: a light, Neo-Romantic work with a lively dance finale and a pretty, often ornate flute line, which Amy Porter played with graceful poise. Derek Bermel, though best known as a composer, is also a fine clarinetist (as well as the orchestra's creative adviser). His contribution here was a rhythmically fluid, rich-hued account of the Copland Clarinet Concerto (1948), written for Benny Goodman, but with fewer concessions to Goodman's jazz virtuosity than to his classical bona fides. In a recent essay on his Web site Mr. Kahane argued that composers are, perhaps cynically, calling straightforward pop songs indie classical works. He said that in his own music, which includes both pop and classical compositions, he preferred to keep the distinctions clear, but that his new "Crane Palimpsest" (2012) - a work in which his artful settings of Hart Crane poems are interwoven with his sophisticated pop responses to the Crane texts - is an attempt to see whether the boundaries of pop could be expanded. If the experiment failed, it was only because Mr. Kahane insisted on categorization. The songs, performed by Mr. Kahane with plaintive directness, are beautifully, often ingeniously, orchestrated. They are popsy but not quite pop, yet not quite classical either. The American Composers Orchestra presents its annual series of Underwood New Music Readings on June 1, 2 and 3 at the DiMenna Center for Classical Music, 450 West 37th Street, Manhattan; americancomposers.org.