Finding the best-suited actors for more than 100 characters (and their understudies) is a year-round project. In order to assemble the best possible casts, Casting Director Bob Mason and Casting Associate Reetu Gowdar need to be familiar with the always-changing talent pool. New actors move to Chicago all the time while others leave the city: they go on tour, move to LA or NYC, and some quit the business. In addition to seeing shows at other Chicago theaters every week and frequently traveling to key theaters across the country, the casting office holds "generals" where actors who are unfamiliar to CST are auditioned. One-day generals are scheduled monthly, and yearly generals take place each January and February. Over the course of two weeks, approximately 500 actors are seen.

At general auditions, actors perform two contrasting monologues or a monologue and a song. New this year, actors are no longer required to perform a monologue from Shakespeare—some actors are reluctant to audition for CST because they don't have verse training. All our actors—even those with a mastery in Shakespearean verse—are provided training and coaching during the rehearsal process. Actors with limited verse experience have always been cast. Felicia Fields (of The Color Purple fame), for example, had never previously performed Shakespeare, and was first cast at CST as the Duchess of York in Barbara Gaines' production of Richard II. Also, a wide variety of styles and non-Shakespeare plays are produced at CST—dramas, plays for young audiences, musicals, even some hip-hop and Kabuki-influenced productions. The casting office needs to be ready, familiar with as many actors as possible, in order to start pulling headshots and calling actors in to audition for specific roles as soon as a play is slated.

Amadeus started rehearsals in early August and the final phase of the casting process began in April. Since director Gary Griffin is from Chicago and is familiar with local actors, he had a list of actors he wanted to audition. In order to have a good mix of new people, too, the casting office prescreened actors by auditioning with scene work from Amadeus, in preparation for auditions with Griffin. Initial conversations helped to define specifically what Griffin wanted in each particular character. According to Mason, "The biggest thing preparing for a show is getting the director to be as specific as they can be so that you really are bringing in the kinds of actors they are looking for." However, this is an evolving process, and as decisions are made other choices are affected. "You can't cast Constanze, Mozart's wife, until you've cast Mozart," Mason explains. "You can have all sorts of ideas about who would be the best, but you are really looking for the one who is the most right for your Mozart, as opposed to who was the best. You find out there is no such thing. It's not that 'She's the best,' it's that 'She's the best in this context.'"