Trial by Jury was Gilbert and Sullivan's second collaboration. Their first, Thespis, (1871) was a Christmas pantomime that was more popular than most such efforts (about 80 performances) but since the music has been lost, we'll never know what most of it was like.
Trial by Jury (1875) was written as a curtain raiser for an existing opera company, probably for (believe it or not) Lohengrin. It was based on some material Gilbert had already written, and when he read it to Sullivan, he found it extremely amusing and set it to music in about 3 weeks. It is the only one of their shows to contain no dialog. The entire short piece is a series of lively songs and choruses.
In the story, Edwin is being taken to court by Angelina who is suing him for breach of promise of marriage. Edwin is much the innocent here, since he thinks he can just explain that he lost interest in her. Nearly everyone else has some ulterior motives. The Judge admits he rose to his position by marrying a "rich attorney's elderly, ugly daughter." He also admits that once he was successful, he threw her over. Like every other man in the courtroom (including the jury) the judge is much taken with Angelina and will do anything to gain her favor. Angelina, on the other hand, mainly wants to use her wiles to get Edwin's money.
Edwin notes that he would make a poor husband, since he "smokes like a furnace, and is always in liquor." The judge proposes that they make him tipsy and see if he is indeed abusive. Edwin doesn't object, but his Counsel does. The judge in exasperation says he will marry her himself, and all ends happily.
Trial by Jury was enormously successful, running for over 300 performances, and led directly to the ongoing partnership between England's greatest comic playwright and one of England's leading composers. As Gayden Wren notes, It was the turning point where "Gilbert and Sullivan" became "Gilbert & Sullivan."
The pair's first full-length operetta, The Sorceror (1877), was moderately successful, running for 178 performances, and it allowed them to begin working in partnership and developing their interactive writing style. However, it was HMS Pinafore (1878) that made them famous. Pinafore was a smash hit, running for 571 performances in London alone, and it became a popular craze in both England in the US (where 8 bootleg companies put on New York performances, before the pair brought their own company over to cash in on this success.)
HMS Pinafore is a satire of love among ranks and of incompetent politicians. Sir Joseph Porter, as First Lord of the Admiralty has never gone to sea, and obtained his political position by apple polishing rather than innate ability. He is consciously modeled on W. H. Smith, the bookstore magnate, who was the real First Lord of the Admiralty, even though he had no naval experience at all. Smith was called "Pinafore Smith" for the rest of his life.
As the story opens the crew of the HMS Pinafore is happily singing and salutes their popular, democratic captain. ("I am the Captain of the Pinafore.") The seaside vendor, Little Buttercup comes on board selling food and trinkets and when the young hero Ralph Rackstraw appears, she indicates that there is a secret behind him that only she knows. Sir Joseph arrives with his retinue of sisters, cousins and aunts and tells of how he rose to the rank of First Lord by polishing the handle of the big front door of his attorney's firm ("When I was a Lad"). The Captain has promised his beautiful daughter Josephine to Sir Joseph, but Josephine secretly loves Ralph Rackstraw, a lowly sailor.
Josephine tells Ralph he should refrain from loving her ("Refrain Audacious Tar") because of the disparity of their ranks, while to the side exclaiming how much she actually loves him. Ralph tells his messmates he has been rejected, and threatens to end it all, but at the last moment Josephine enters declaring her love. They plan to sneak off to be married, but ugly Dick Deadeye warns that it will never work because she is a Captain's daughter and he a lowly tar. However, the chorus thrusts him away and thy first act ends happily and a series of rousing choruses as they sing of their plans.
In the second act, the Captain sings of the changes taking place (Fair Moon) and Buttercup comes to warn him that "Things are Seldom What They Seem." Sir Joseph tells the Captain that Josephine shouldn't be so reticent to be attracted to him, since it is official policy that love levels all ranks. They sing the rousing Bell Trio ("Never Mind the Why and Wherefore"). Deadeye comes to warn the Captain of the impending elopement ("Kind Captain") and the Captain catches them as they are sneaking away, uttering an injudicious "Damme" that shocks everyone. Sir Joseph in hearing of Ralph's intent banishes him to the dungeon. But then Buttercup reveals that the Captain and Ralph had been switched at birth. The Captain is now a seaman and Ralph the captain. Thus, Josephine is now too low a rank for Sir Joseph, and Ralph and Josephine are free to marry. The Captain can now marry Buttercup since rank no longer separates them, and Sir Joseph can marry his cousin Hebe and all ends happily.
To Read More, see: A Most Ingenious Paradox : The Art
of Gilbert & Sullivan,
by Gayden Wren, Oxford University Press, 2001