Opening on Broadway on October 10, 1947, the musical centers on the life of Joseph Taylor Jr., who follows in the footsteps of his father as a doctor, but is tempted by fortune and fame at a big-city hospital.

After a disastrous tryout in New Haven, Connecticut, the musical opened on Broadway to a large advance sale of tickets, and very mixed reviews.

In March, Hammerstein approached Rodgers with the idea for a play with two men as the central characters, rather than the usual "boy and girl" format.

By September, the general theme for the story had been established: the struggle of the main character to avoid compromising his principles as he progresses in life.

[5] He wrote a few pages of the book before embarking with his wife for Australia to visit his mother-in-law; when his ship arrived in Brisbane he mailed Rodgers part of the remainder.

[7] Hammerstein's protégé Stephen Sondheim, who served as a $25-a-week gofer on the production, stated, Years later, in talking over the show with Oscar—I don't think I recognized it at the time—I realized he was trying to tell the story of his life ... Oscar meant it as a metaphor for what had happened to him.

When a few days before rehearsals began, she asked Hammerstein what the show was about, the lyricist replied, "It's about a man not being allowed to do his own work because of worldly pressures.

Instead of conventional sets, locations were suggested by platforms, images projected onto backdrops, and lighting—there were 500 lighting cues, at the time a Broadway record.

There were forty stagehands, needed to shift sixty partial sets, with objects moved onto the stage by a semicircular track hidden by an elaborate series of curtains.

According to de Mille biographer Carol Easton, "Allegro was a leviathan of a show, on a scale exceeding the grasp of any individual.

"[13] However, Rufus Smith, who played the minor role of the football coach, stated, "Never again in my life will I experience what it is like to stop a show cold, by doing exactly what she taught me".

During the first act, William Ching, playing Joseph Taylor Sr., was singing "A Fellow Needs a Girl" when the scenery wall began to collapse, forcing him to hold it up until the stagehands noticed.

Next night she comes back, came to the same point in the song, and starts to fall, and the entire audience gasps because they'd all read the Herald Tribune.

"[16] The disasters of the New Haven opener concluded during "Come Home", a song near the end of the play—the quiet urgings of the chorus and Joe's mother to entice him to return to his small town.

The elder doctor has less time for a nurse, Carrie Middleton, who has worked at his hospital for thirty years and once dated him, but who is involved in a labor protest—Denby orders her fired at the request of Lansdale, an influential trustee and soap manufacturer.

At a dedication of a new pavilion at the hospital, Joe has a revelation and shifts the path of his life; as he does so, Grandma appears and calls for Marjorie to come watch, an echo of the scene in which he learned to walk.

[26] In March 1994 a staged concert version was presented by New York City Center Encores!, with a cast that included Stephen Bogardus (Joseph Taylor Jr.), Karen Ziemba and Jonathan Hadary.

[28] A revised version of Allegro, re-written by Joe DiPietro, who was a protege of Oscar's son James Hammerstein, was produced at the Signature Theatre (Arlington, Virginia) in January 2004.

The show received its European première in a revival that took place at the Southwark Playhouse, London UK, running from August to September 2016 to positive reviews.

[33] A studio recording of the complete score was made in 2008, with an all-star cast featuring Patrick Wilson as Joe, Nathan Gunn and Audra McDonald as his parents, Marni Nixon as Grandma, Laura Benanti as Jennie, Liz Callaway as Emily, Judy Kuhn as Beulah, Norbert Leo Butz as Charlie, with special appearances by Stephen Sondheim, Schuyler Chapin and, through archival audio recordings, Oscar Hammerstein.

[34] According to musical theatre author John Kenrick, "this all star studio cast glorifies all that is right with this melodious and sometimes adventurous score".

The New York Times critic Brooks Atkinson opined that Rodgers and Hammerstein had "just missed the final splendor of a perfect work of art".

[21] Robert Coleman of the New York Daily Mirror stated that "Allegro is perfection",[20] and added that it was "a stunning blending of beauty, integrity, intelligence, imagination, taste and skill ... it lends new stature to the American musical stage".

[20] Critic George Jean Nathan, in a special piece in the Journal American, decried "such hokum mush as the familiar wedding scene and the ghost of a mother who returns at intervals to keep her son from error, but a cocktail party chatterbox number paraphrased from an old Noël Coward movie, a college number dittoed from an earlier George Abbott one, and various other elements hardly rivaling the daisy in freshness".

"[39] De Mille's direction and choreography were reviewed generally positively; Cecil Smith applauded her for the "ease and flawless design with which Miss de Mille brings mobility to these non-dancing [singing and speaking choruses] ... no previous musical has approached Allegro in consistency of movement, expertness of timing and shapeliness of visual patterns.

[40] Times dance critic John Martin stated, "Allegro has definitely made history" for de Mille's giving "form and substance to material with little of either".

The lyricist objected, pointing out that the worst character in the musical was a small-town girl, but according to Hammerstein biographer Hugh Fordin, "he knew it was his fault that the message was not clear.

"[42] A decade after Allegro's premiere, after learning of his terminal cancer, Hammerstein returned to the musical, hoping to correct its flaws, but he did not complete the project.

[45] Rodgers further defended the play, "The comments we made on the compromises demanded by success, as well as some of the satiric side issues—hypochondria, the empty cocktail party—still hold.

Author James Michener recalled his meeting with the duo over the possibility of converting his book Tales of the South Pacific into a musical.