Following West Side Story, Bernstein would join forces with Sondheim and Robbins for an experimental work that deepens the connection of his music theater aesthetic to Weill. It was Robbins who had the idea of reinventing one of Brecht's Lehrstücke, or didactic plays, for performance on Broadway after directing and co-producing (to financial loss) Mother Courage and Her Children together with Cheryl Crawford in 1963. He landed upon The Exception and the Rule (Die Ausnahme und die Regel, as translated by Eric Bentley), a work with an unusual performance history. The play was first performed in the Hebrew language at a kibbutz in 1938 with music by Nissim Nissimov and subsequently set to music by Paul Dessau a decade later. A 1965 off-Broadway production featured incidental music by Stefan Wolpe.

Sondheim had declined the opportunity to write the book, music and lyrics for The Measures Taken on the basis of what he later recalled as “Brechtophobia” but saw more potential in Exception. After writing two songs, however, he decided that his “heart wasn't in them” and suggested Bernstein as a collaborator for both music and lyrics. When Bernstein declined, Robbins invited the lyricist Jerry Leiber. But he would be replaced by the playwright John Guare, enticing Sondheim to rejoin after he learned of his plans to set the play within a television studio: “The Brecht play would be chopped up into scenes that would be interrupted by the conflicts among the cast in the studio and thus not be so relentlessly Brechtian,” explains Sondheim.

The original Exception explores the erosion of human values in a capitalist rat race. The oil merchant Karl Langman hires a Guide and a Coolie, or porter, to help him cross an uninhabited desert and reach the fictional city of Urga. After firing the Guide, he and the Coolie lose their way. When the Coolie offers Langman (the Merchant) a sip of water, he believes he is about to strike him and fatally shoots him. Langman claims in trial that he acted in pre-emptive defense and is acquitted by the court. As the Guide admonishes in the final scene, “Try to do a generous deed/You’ll be the loser./Fear for the man who shows/A friendly nature!”

Robbins reinvented the story as a commentary on tensions between Caucasians and African-Americans, casting the Merchant as not just a ruthless businessman who is above the law but a racist.