To most of the world, Radiohead and Johannes Brahms may seem like strange bedfellows — a critically hailed British alternative rock band and an iconic German pianist and composer who's been dead 118 years. Why lump those two together?To Steve Hackman, though, the connections are obvious."When you boil them down, Radiohead and Brahms are made of the same 12 notes," the composer and arranger said during a recent phone interview. "When treated that way — when treated with some sort of classical precision and technique — a compelling marriage can be made that will be fun for musicians to play."Hackman is the creator of Brahms v. Radiohead, an orchestral mash-up of Brahms' Symphony No. 1 and Radiohead's 1997 album OK Computer, two beloved European masterpieces released 121 years apart. On Friday, he'll conduct the piece for the fifth time live with the Florida Orchestra in St. Petersburg.To be clear: This is not a pops show. Brahms v. Radiohead incorporates elements from both artists into an all-new, hourlong arrangment of vocals and traditional symphonic orchestration. It may surprise fans of the band how naturally singles like Paranoid Android and Karma Police weave into and out of Brahms' First, but to Hackman — who crafted the piece by immersing himself in both artists' music, then sittting down at a piano to pick out commonalities — Brahms and Radiohead are a perfect fit. "I think it's the chromaticism of both, the pathos of both, and the balance and tension and relief of both," said Hackman, 34. "You always feel that tension, the undercurrent of a longing, a melancholy, a vibe."It also makes for some fascinating transitions. For example: Toward the end of Brahms v. Radiohead, Hackman drifts from the dire, desperate Exit Music (For a Film) into the triumphant, hopeful intro to Symphony No. 1's fourth movement. "It's almost a frightening introduction to the fourth movement, almost like an opera overture, and then (Brahms) moves to a beautiful, regal C-major horn theme," Hackman said. "Really, it's kind of his plan. I was just inserting a Radiohead song that is just as frightening as this Brahms music. The light vs. dark was already in there; I just threw more dark in there."Hackman, a Chicago native now based in New York, grew up adoring the Beatles and the jam band Phish, and discovered Radiohead in college. "All my life it's really been kind of two parallel listening paths of classical music and 'popular' music," he said. As Hackman studied classical composition and conducting, he retained his deep respect for rock composition. In addition to Brahms and Radhiohead, he's mashed up Coldplay with Beethoven and Bon Iver with Copland, and crafted arrangements of works by artists like John Mayer, Mumford and Sons and Daft Punk. He's also a singer — he once made it to Hollywood on American Idol — with grand pop ambitions of his own. In 2014, under the moniker Stereo Hideout, he released The Radio Nouveau, a schizophrenic collection of kitchen-sink electro-pop that saw Hackman not just singing but rapping. All of this helps Hackman stand out in the often stodgy world of classical composition, where "there's such a stigma associated with pop and rock music," he said. Whereas rock fans may come to Brahms v. Radiohead eager to embrace the unique symphonic mash-up ("Radiohead fans tend to be creative, open-minded, thinking-outside-the-box-type people"), many classical fans, and even some musicians, are not."It's very important that it's arranged and crafted in a virtuosic way, so that it is worthy of their skills," he said. "Those with an open mind, and those that share my belief that all music is created equal, come away with it having had a very valuable experience, maybe an eye-opening experience, and they may say, 'I'm going to check Radiohead out. This sounds cool.'"