The Sound of Music is a musical with music by Richard Rodgers, lyrics by Oscar Hammerstein II, and a book by Howard Lindsay and Russel Crouse. It is based on the 1949 book The Story of the Trapp Family Singers by Maria von Trapp. Set in Austria on the eve of the Anschluss in 1938, the musical tells the story of Maria, who takes a job as governess to a large family while she decides whether to become a nun. She falls in love with the children, and eventually their widowed father, Captain von Trapp. He is ordered to accept a commission in the German Navy, but he opposes the Nazis. He and Maria decide on a plan to flee Austria with the children. Many songs from the musical have become standards, including "Do-Re-Mi", "My Favorite Things", "Edelweiss", "Climb Ev'ry Mountain", and the title song "The Sound of Music".

The original Broadway production, starring Mary Martin and Theodore Bikel, opened in 1959 and won five Tony Awards, including Best Musical, out of nine nominations. The first London production opened at the Palace Theatre in 1961. The show has enjoyed numerous productions and revivals since then. It was adapted as a 1965 film starring Julie Andrews and Christopher Plummer, which won five Academy Awards, including Best Picture. The Sound of Music was the last musical written by Rodgers and Hammerstein, as Oscar Hammerstein died of stomach cancer nine months after the Broadway premiere.

After viewing The Trapp Family, a 1956 West German film about the Trapp family, and its 1958 sequel (The Trapp Family in America), stage director Vincent J. Donehue thought that the project would be perfect for his friend Mary Martin; Broadway producers Leland Hayward and Richard Halliday (Martin's husband) agreed. The producers originally envisioned a non-musical play that would be written by Lindsay and Crouse and that would feature songs from the repertoire of the Trapp Family Singers. Then they decided to add an original song or two, perhaps by Rodgers and Hammerstein. But it was soon agreed that the project should feature all new songs and be a musical rather than a play.

Details of the history of the von Trapp family were altered for the musical. The real Georg von Trapp did live with his family in a villa in Aigen, a suburb of Salzburg. He wrote to the Nonnberg Abbey in 1926 asking for a nun to help tutor his sick daughter, and the Mother Abbess sent Maria. His wife, Agathe Whitehead, had died in 1922. The real Maria and Georg married at the Nonnberg Abbey in 1927. Lindsay and Crouse altered the story so that Maria was governess to all of the children, whose names and ages were changed, as was Maria's original surname (the show used "Rainer" instead of "Kutschera"). The von Trapps spent some years in Austria after Maria and the Captain married and he was offered a commission in Germany's navy. Since von Trapp opposed the Nazis by that time, the family left Austria after the Anschluss, going by train to Italy and then traveling on to London and the United States. To make the story more dramatic, Lindsay and Crouse had the family, soon after Maria's and the Captain's wedding, escape over the mountains to Switzerland on foot.

In Salzburg, Federal State of Austria, just before World War II, nuns from Nonnberg Abbey sing the Dixit Dominus. One of the postulants, Maria Rainer, is on the nearby mountainside, regretting leaving the beautiful hills ("The Sound of Music"). She returns late to the abbey where the Mother Abbess and the other nuns have been considering what to do about the free-spirit ("Maria"). Maria explains her lateness, saying she was raised on that mountain, and apologizes for singing in the garden without permission. The Mother Abbess joins her in song ("My Favorite Things"). The Mother Abbess tells her that she should spend some time outside the abbey to decide whether she is suited for the monastic life. She will act as the governess to the seven children of a widower, Austro-Hungarian Navy submarine Captain Georg von Trapp.

Maria arrives at the villa of Captain von Trapp. He explains her duties and summons the children with a boatswain's call. They march in, clad in uniforms. He teaches her their individual signals on the call, but she openly disapproves of this militaristic approach. Alone with them, she breaks through their wariness and teaches them the basics of music ("Do-Re-Mi").

Rolf, a young messenger, delivers a telegram and then meets with the eldest child, Liesl, outside the villa. He claims he knows what is right for her because he is a year older than she ("Sixteen Going on Seventeen"). They kiss, and he runs off, leaving her squealing with joy. Meanwhile, the housekeeper, Frau Schmidt, gives Maria material to make new clothes, as Maria had given all her possessions to the poor. Maria sees Liesl slipping in through the window, wet from a sudden thunderstorm, but agrees to keep her secret. The other children are frightened by the storm. Maria sings "The Lonely Goatherd" to distract them.

Captain von Trapp arrives a month later from Vienna with Baroness Elsa Schraeder and Max Detweiler. Elsa tells Max that something is preventing the Captain from marrying her. He opines that only poor people have the time for great romances ("How Can Love Survive"). Rolf enters, looking for Liesl, and greets them with "Heil". The Captain orders him away, saying that he is Austrian, not German. Maria and the children leapfrog in, wearing play-clothes that she made from the old drapes in her room. Infuriated, the Captain sends them off to change. She tells him that the children need him to show his love for them, and he angrily orders her back to the abbey. As she apologizes, they hear the children singing "The Sound of Music", which she had taught them, to welcome Elsa Schraeder. He joins in and embraces them. Alone with Maria, he asks her to stay, thanking her for bringing music back into his house. Elsa is suspicious of her until she explains that she will be returning to the abbey in September.