Gene Kelly did not receive an Oscar nomination for portraying E.K. Hornbeck in Inherit the Wind.
Kelly plays his part as a cynical showman, and actually he uses well his usual screen persona well refuting it in a way at the same time. He of course as the same voice, and one could argue almost the same delivery as in his musicals as Hornbeck, but with Hornbeck there is always an underlying deep rooted cynicism that always prevails. Kelly infuses every line he has with a great deal of enthusiasm and well showmanship, but below everything that he says there is always an unmistakable amount of venom within it.
This is a fairly limited role for Kelly actually after his speeches early in the film he mostly just has a quick reaction that only ever is brief, which is especially true in the court room scenes where he takes a back seat. That is not to say Kelly is forgotten, and he is good in coming in whenever he can bringing about the sharp wit of his character very well. He does not do a great deal though more until the end when Spencer Tracy's character questions his cynicism. Kelly is quite good in this scene as he shows Hornbeck feign any feelings of self-doubt, and quickly go back to his old ways. This is a pretty simple, Kelly does play it well though, and it shows that he had more in him than the Gene Kelly musical character.