Elvis Presley's band in the film is his real-life band including Scotty Moore on electric guitar and Bill Black on stand-up bass. Both had been with Elvis since his beginning in Memphis at Sun Records (owned by Sam Phillips). In the recording studio scenes, the piano player is Mike Stoller of the Lieber (Jerry Lieber and Stoller songwriting team, which wrote many of the major hit rock songs of the 1950s.
Originally choreographer Alex Romero created a dance for the song "Jailhouse Rock" that was in a style apropos for a more classically trained dancer than Elvis Presley. When Romero realized that his plans for the number were never going to work, he asked Elvis how would he normally move to the song, leading Elvis to become the uncredited choreographer for what many consider his most famous dance number in all of his movies.
Jerry Leiber and Mike Stoller wrote four songs ("Jailhouse Rock", "I Want to Be Free", "Treat Me Nice" and "You're So Square") in five hours after their music publisher, under deadline, locked them in their hotel room.
The film was not actually shot in widescreen. It was converted to CinemaScope in the final print after having been shot in standard Academy ratio, much like some films which are "matted" after having been shot in Academy ratio. The process used was contemporary of Superscope and a forerunner of Super 35. It was filmed using spherical lenses at an aspect ratio of 1.37:1. In the printing process, the images were cropped to a height of 2 perforations giving them an aspect ratio of 2.36:1. The images were then stretched vertically to a height of 4 perforations, at which point they conformed to the standard CinemaScope-2 format.
In the lawn party scene, just after Vince embraces an unresponsive Peggy, the hired orchestra begins an instrumental number. The tune they're playing is "All I Do Is Dream Of You", from the film Sadie McKee (1934). This same tune, with vocal accompaniment, was featured in a series of television commercials for Bell Canada during the mid-'70s.