Director Walter Hill envisioned the film's climax to be like a boxing match, or a blues version of The Karate Kid (ironically, also starring Macchio). With that in mind, the original guitar "duel" was recorded; it was a battle between Roth and Ry Cooder, with the plan that Cooder would appear on screen in the role of Jack Butler. As the film progressed, however, the producers were growing less keen on this idea and wanted someone else for the part, much to the disappointment of Cooder. Nonetheless, Cooder was still musical director and therefore was tasked with finding a replacement. Keith Richards, Frank Zappa and Stevie Ray Vaughan were briefly considered for the role, but ultimately with the producers keen on capitalizing on the mid-Eighties “guitar shred” boom, Steve Vai was cast and was quickly able to put his own stamp on the part. It is largely based on Niccolo Paganini's Caprice #5. This was skillfully connected to the story, as according to myth, much like Robert Johnson, Paganini apparently sold his soul to the devil in exchange for his musical skills.