Opera legend Maria Callas in the supreme diva role, Norma
"Opera is when a guy gets stabbed and instead of bleeding, he sings."
— Ed Gardner
Opera has been around since the end of the 16th century and still going strong. Major opera composers include Mozart, Handel, Verdi, Gioachino Rossini, Wagner, Puccini and Richard Strauss, though there are, of course, many more.
The public perception of the difference between opera and The Musical is that musical theatre has breaks for spoken dialogue, whereas opera is "sung through", alternating between "arias" (big numbers) and "recitative" (music written in the style and rhythm of dialogue). While not a bad approximation, it's also not true. There are a number of Sung Through Musicals, such as Les Misérables and Joseph and the Amazing Technicolor Dreamcoat, or ones that are nearly so, like The Phantom of the Opera and RENT (which in fact has more Wham Lines spoken than sung!). Likewise, several opera, like The Magic Flute and Carmen, involve spoken dialogue. The actual line between musicals and opera is blurry and kind of technical, but the short of it is that opera doesn't use electronic sound equipment and musicals typically need better actors than singers. Stephen Sondheim was heard to claim, "I really think that when something plays Broadway it's a musical, and when it plays in an opera house it's opera. That's it."
The public perception of opera is that it's always a tragedy. This is also not true; the opera genre is as varied as any other. Many operas are comedies, and even the serious ones tend to have at least some humorous parts. In fact, during the Baroque and Classical periods, operas were generally expected to have happy endings; the concept of tragic operas only became popular during the Romantic period. And while some operas have incredibly well-crafted lyrics and story lines that are true works of art, others are... not quite as brilliant.
That said, the opera genre is known for featuring many a work with extremely drawn-out texts focusing on a single (often trivial) theme. As a result, opera texts (libretti) are often mocked, and in many cases it's mainly the quality of the music that makes an opera work, along with the same thing you need for any theatrical production: committed performers bringing the art form to life on stage. Movies have car chases, rock songs have guitar solos, and operas have death-arias (the soprano frequently dies). In fact, both Anna Russell and B.J. Ward (in her one-woman show, Stand-Up Opera) have made entire comedy routines of poking fun at opera tropes.
Nowadays we tend to think of operas as high-falutin' fare for the nobs and snobs. Back in the 18th, 19th, and early 20th centuries, though, opera was popular music, to the point that the opening night audience was chock-full of transcriptionists. And it didn't take long for them to produce a saleable product: Rossini once said that by the time he left the opera house for home at the end of opening night, hawkers would be lined up on the street selling copies of the music and lyrics of his arias to those who couldn't afford a ticket.
Several modern films and other works have been created as operas (that is, entirely consisting of sung dialogue). The most famous "serious" opera film is probably The Umbrellas of Cherbourg, starring Catherine Deneuve. A very modern example is Repo! The Genetic Opera, which transplants the style into industrial sci-fi horror. The term Rock Opera is thrown around at times for a sub-genre of the themed Concept Album, but most "rock operas" are not produced for the stage (with an exception or two). The nearest thing to a modern successor to opera is Broadway-style Musical Theater. Indeed, musicals can trace their origins to opera through the operatic subgenre of operetta or light opera, which, as its name implies, is light in terms of subject matter (i.e. it's funny) and music, and often feature a good deal more plain dialogue than ordinary operas. The works of Gilbert and Sullivan are generally considered transitional, as while they considered their works to be comic operas, they would probably be called musicals if produced today; many would argue that musicals are basically the genre of theatre launched by G&S.
Used in movies and TV shows to add a touch of class. Or just something artsy. Or for the cast to get bored and fall asleep, which is something that can't be done (too loud).
Not to be confused with the Cantata, though at least one cantata, Johann Sebastian Bach's Coffee Cantata, can be considered a miniature comic opera according to The Other Wiki.
All There in the Manual Without a program, good luck trying to understand what's going on on stage. Many modern opera houses (Especially in Germany) show the text right above the stage, and some fancy opera houses even have a small screen on the back of the seats with the text in several selectable languages. Performing opera in translation has disadvantages too. It's often just as hard to make out the words, and when you can the effect isn't always what it might be. For example, to an English ear Tosca (in one of the rare operas with a stonking good story) may sound dramatic when she sings 'Muori! Muori! Muori! ... È morto.' but translated into English this becomes 'Die! Die! Die! ... He's dead.' 'Nuff said.
All Musicals Are Adaptations: Opera gets this from both sides. Many operas are adaptations of existing works, and a number have been adapted into modern musicals.
Brawn Hilda: A rather unfortunate stereotype of opera singers (as in the saying, "It ain't over till the fat lady sings"). Although it's usually very exaggerated, it does have a degree of Truth in Television since the vocal pipes necessary to support a huge operatic voice often go along with a larger frame. The trope may have originated from Wagner's Die Walküre, where the main character, Brünnhilde, is often played by an imposing woman. Though if you think that means opera singers are unattractive, think again.
If you're watching work from the 17th or 18th century (where opera houses and orchestras were much smaller) this is usually averted, if not sometimes inverted- soubrette sopranos who play roles like Despina or Zelina (or anything else written for Nan Strorace) are usually quite small women, cast for their girlish vocal instrument. Women in 'trouser roles' in these operas are likewise often petite.
And on the subject of Rossini, Constantino Dall'Argine did a version of The Barber of Seville that was first performed two days before Rossini died. History repeated itself and Dall'Argine's work disappeared forever.
Leon Kirchner had his operatic career destroyed from the get-go, where Lily gave one of the quickest bailouts in operatic history.
Crosscast Role: There are many "trouser roles" for women playing men and several "skirt roles" for men playing women. In the Baroque period (Opera's earliest century-and-a-half), especially in those areas where the pope's influence was strongest such as Rome, female roles were often played by male castrati. (And, yes, a castrato is exactly what you think it is.)
Dawson Casting: Due to the physical requirements and amount of training involved, teenage characters like Cio-Cio-San (Madama Butterfly) or Salome are almost always portrayed by singers in their twenties or older. And teenage boys are generally played by adult women, usually mezzo-sopranos. Sometimes averted with less demanding roles such as Barbarina from The Marriage of Figaro, who is occasionally played by a high-school aged singer.
Everyone Is Jesus in Purgatory: Individual operas may very well be subject to this, but the entire form of Opera is actually a product of this. In attempting to revive classical Greek plays to the theatre of the Renaissance era, interested scholars decided that the Greek plays were meant to be sung in their entirety. New works followed suit, and the rest is history.
David Merrill: You're the rat again, aren't you, Daddy?
Robert Merrill, baritone: The baritone is always the rat, my boy.
The darker and heavier the voice, the meaner and nastier the villain.
In the Baroque period, heroic roles were often written for castrati, whose unbroken voices were synonymous with virtue and heroism on the opera stage. The broken normal male voice was usually assigned to villains or servants.
A lament of altos (the lowest and darkest of female voices) is that alto roles are always either "bitches, britches, or witches".
Farce: The plot of many comic operas. There's even a whole genre called "opera buffa" (to distinguish it from "opera seria"). Notable examples are The Marriage of Figaro, The Barber of Seville, and L'elisir d'amore, all of which are screamingly funny provided the cast is on their toes.
Femme Fatale: All the best diva roles. Special mention goes to Violetta from La Traviata.
Flame War: For all the veneer of civilisation in the genre, opera enthusiasts can get just as vicious in defense of their favourite singers and composers as any other fans. Just go have a look at the comments on any opera clip on YouTube.
Getting Crap Past the Radar: A lot of Mozart. For example, Don Giovanni sings about Zerlina's "honeyed lips", using Italian slang for vagina.
Gratuitous Foreign Language: As mentioned above, it's traditional for operas to be performed in their original language rather than translated.
Groin Attack: In the early days of opera, it was considered improper for women to appear on stage, but there were still treble singers. This was because if a prepubescent boy had a good singing voice, a simple operation could enable him to preserve it permanently into adulthood. Yes, "castrato" means exactly what you think it does. At the time, they often became wildly successful superstars, but the practice fell out of favor by the mid-1800s.
Happily Ever After: Anything by Mozart or Rossini. Rossini has had his share of tragic endings as well, in his lesser known 'serious' operas.
"I Am" Song: "Mi chiamano Mimì", "Io son l'umile ancella", "Largo al factotum della città" among others...
Incredibly Long Note: This and this, for starters. In fact, some famous singers like Birgit Nilsson & Franco Corelli made it a friendly sport over who'd black out first from holding that high C in Turandot. Everyone else peed in excitement, of course. Expect this trope (especially of the soft-but-incredibly-held-out variety) when you see Montserrat Caballé on the cast list or album notes.
Large Ham: Opera has long been full of hammy divas and divos (many roles, and perhaps the very nature of Romantic opera, lend themselves to this), though singers and productions seem to be averting this trope more and more these days, partly thanks to speakers making it no longer necessary to have No Indoor Voice.
Leitmotif: Wagner Wagner commentator Hans von Wolzogen is the Trope Namer, although the concept predated Wagner by quite a while
Love It or Hate It: Richard Wagner. Composer of the finest music and producer of the best plots ever, or overly bombastic and just too damn long-winded? One of the less intelligent criticisms of Wagner is that he was "Hitler's favorite composer". This is kind of unfair; Wagner couldn't possibly have pandered to Hitler in any way, since he died before Hitler was even born. (And of course, Hitler Ate Sugar.)
Melismatic Vocals: Or 'coloratura'. Bread-and-butter for ALL voice, but ideally for belcanto roles. A huge plus if you have a large voice (dramatic coloratura) - although having a large voice and a dramatic voice is not necessarily the same thing.
Lampshaded gloriously in most Baroque operas. Expect the vocal line to fall when singing about sadness or despair, rise up when singing about glory, anger and war, and have crazy roulades when singing about being in love (as in "adrift in a sea of love").
Name's the Same: It helps to be a bit more specific when you're looking for operas by Strauss. Johann Strauss wrote all those lighthearted waltzes, but also several light operas, the only one still regularly performed being Die Fliedermaus; Richard Strauss (no relation) wrote dramatic pieces like Elektra and Salome. (Johann Strauss is also not to be confused with his father, Johann Strauss Sr., or his brother, Josef Strauss...)
Necessary Weasel: The entire audience, including the rearmost, who are usually 50m or more from the stage, have to understand who the disguised character is.
One-Hit Wonder: Pietro Mascagni and Ruggero Leoncavallo fall into this category respectively with Cavalleria Rusticana and I Pagliacci. Composers who only wrote one opera include:
Béla Bartók: Duke Bluebeard's Castle
Ludwig van Beethoven: Fidelio
Paul Dukas: Ariane et Barbe-bleue (three other operas are now lost)
Franz Liszt: Don Sanche—and it was a collaborative effort written, no less, when he was in his teens.
Jean Sibelius: The Maiden in the Tower, composed to a Swedish libretto, first performed in Helsinki.
Power Echoes: The Valkyries from Die Walküre were originally conceived as singing their entrance war-cry off-stage into actual megaphones ('singing trumpets'). Played straight in Siegfried with the dragon.
Recycled Script: Several examples, but Rossini was particularly well known for lifting music from one of his operas to another. It was acceptable at the time, as long as the two works didn't premiere in the same town.
Rule of Drama: The meeting of the queens in Donizetti's Maria Stuarda, just to name one example.
Rule of Three: Many operas have three acts, especially those of Wagner. For Verdi and Puccini, their third operas (respectively with Nabucco and Manon Lescaut) formally launched their careers.
Satellite Love Interest: Very common - as in the Commedia dell'Arte, viewers are given little explanation as to who the inamorati actually are. They're young and in love, which usually sums up both characters' entire personalities (or at least the soprano's).
Tear Jerker: Some operas, especially ones by Puccini, seem engineered specifically to be as heart-rending as possible.
That Makes Me Feel Angry: In opera, this trope is pretty much a must-have, since the music is more important than the words and many singers don't bother acting things out too much. Opera is full of (insert adjective here) mi sento and other status-descriptions. Or the composer/librettist put it in to give the singer an indication of how the character should feel; singers are expected to act nowadays. Also, during the Baroque era, musical drama tended to be structured according to the so-called doctrine of affects, with consecutive numbers depicting contrasting emotions - a lilting love duet followed by a furious vengeance aria, for instance. If the idea is to juxtapose readily identifiable emotions for maximum effect, it makes sense to flag them in the libretto.
Theme Naming: Ariane et Barbe-bleue was written by Maurice Maeterlinck, who named Bluebeard's five former wives after female characters in his own plays: Mélisande from Pelléas et Mélisande, Alladine from Alladine et Palomides, Ygraine and Bellangère from La mort de Tintagiles, and Sélysette from Aglavaine et Sélysette.
Willing Suspension of Disbelief: Pretty much a given for all operas ever. Many plots are completely implausible, The Casanova is often played by a short, fat, middle aged guy, The Ingenue is often played by a tall, buxom woman, and there's only so much costuming can do. Opera is pretty much built on this trope - generally, the audience is there for the music.
It also creates a certain amount of Colorblind Casting, since the voices are usually cast indiscriminately of the singer's race.
Heavenly Creatures: Toward the end, just before the tragic finale, Juliet stands on her balcony and sings "Sono andati" (Are they gone?) from La Boheme. It's actually Kate Winslet singing. On the fatal walk, the Humming Chorus from Madama Butterfly is heard. It creates an unbearable dramatic tension, especially if you know the story.