Composer John Stevens, a professor of tuba and euphonium at the University of Wisconsin-Madison, had CSO principal Gene Pokorny in mind when he wrote Journey, his concerto for contrabass tuba: Pokorny is a “foamer”–a rail buff who chases steam locomotives–and Journey’s chugging finale sounds like a train at full speed. The concerto, premiering at these performances, also pays homage to Arthur Honegger’s 1923 tone poem Pacific 231; though Honegger didn’t feature the tuba the way Stevens has, he claimed to love trains as other men loved women, and used the orchestra to imitate screeching brakes and hissing steam. Though the tuba is notoriously unwieldy, Pokorny is agile and accurate across its entire five-octave range, even the basement notes no other brass instrument can hit. When Daniel Barenboim went to Berlin three years ago to conduct the Ring cycle, he took Pokorny with him–a special honor for a tubaist, since Wagner’s sprawling masterwork makes such demands of the instrument that he designed a hybrid horn, now all but obsolete, to meet them. Pokorny has also played in sound-track orchestras for films like Jurassic Park and The Fugitive–and Journey is as pictorial as most movie scores, with staggering climaxes, comic relief (a nod to Pokorny’s fondness for the Three Stooges), lyrical interludes, and melodic cadenzas in which the soloist plays the role of the train’s passenger. It’s not too often that a tubaist gets a chance to come out from behind the rest of the orchestra and sit next to the podium, but in this case it should be worth the wait, for the audience as well as for Pokorny. William Eddins conducts this all-American program, which also includes Copland’s Symphony no. 3, in observance of the composer’s 100th birthday, and the Symphonic Dances from Bernstein’s West Side Story. Thursday through Saturday, June 8 through 10, 8 PM, Orchestra Hall, Symphony Center, 220 S. Michigan; 800-223-7114 or 312-294-3000. TED SHEN