Il mondo della luna (The World in the Moon), Hob. 28/7, is an opera buffa by Joseph Haydn with a libretto by Carlo Goldoni, first performed at Eszterháza, Hungary on 3 August 1777. It was first written for the composer Baldassarre Galuppi and performed in Venice in the Carnival 1750, then adapted for Haydn's version of the opera for the wedding celebrations of Count Nikolaus Esterházy, the younger son of Haydn's patron, Prince Nikolaus Esterházy. Goldoni's libretto had previously been set by four other composers. It is sometimes known by its German title Die Welt auf dem Monde.
Role Voice type Premiere Cast, August 3, 1777
(Conductor: Joseph Haydn)
Ecclitico, a would-be astrologer tenor
Ernesto, a cavalier baritone (originally male soprano) Pietro Gherardi
Buonafede bass Benedetto Bianchi
Clarice, daughter of Buonafede soprano Catarina Poschwa
Flaminia, another daughter of Buonafede soprano Marianna Puttler
Lisetta, maid of Buonafede mezzo-soprano
Cecco, servant of Ernesto tenor Leopold Dichtler
Four scholars and noblemen
The roles of Ecclitico and Lisetta were written for Guglielmo Jermoli and his wife Maria Jermoli, but they left Eszterhaza shortly before the premiere.
The opera is scored for two oboes, two bassoons, two horns, two trumpets, timpani, strings, continuo.
Please help improve this article by expanding it. Further information might be found on the talk page. (May 2008)
A terrace in the house of the bogus astronomer Ecclitico; an observatory tower with a telescope. A starlit night, with full moon
Despite its overall playful character, the opera sets off in a serious tone. Ecclitico and his four students sing a hymn to the moon, which can be noted for its simple grace. Ecclitico boasts of how he can dupe the foolish. Buonafede appears to ask for explanations: a complete verdant that he is, he does not have a clue what the Moon is. Ecclitico explains to him that through his super-strong telescope he will be able to see the Moon's transparent surface all the way through the houses and will be capable of spying on the ladies that undress before going to bed. Buonafede then attempts to view the moon through Ecclitico's telescope whilst simultaneously Ecclitico's servants move caricatures in front of the telescope's lens. The fetch works to the point that Buonafede describes what he thinks he has seen: a very beautiful young girl caressing an old man, a husband ready to punish his wife for her infidelity, and a man that completely dominates his female lover. He rewards Ecclitico with some coins and leaves. Alone now, Ecclitico muses that it is not the old man's money he wants, but to wed his daughter Clarice. Ernesto, a nobleman who is in love with Clarice's sister Flaminia and his servant Cecco (in love with Buonafede's servant, Lisetta) now join Ecclitico. Buonafede, instead, intends to marry them off to rich suitors. Ecclitico assures Ernesto and Cecco that with a little money all their difficulties will be solved. In a more serious aria ("Begli occhi vezzosi"), Ernesto dreams of Flaminia's eyes and awaits impatiently the moment in which the two of them will set out to live together. Cecco, on his part, is convinced that everyone's pretending and insistingly points out the comic side of life.
A room in Buonafede's house
Clarice and Flaminia, the two sisters, dream of escaping their tyrannical father. In a long aria, almost in the style of an opera seria, Flaminia recognises that even if reason is to dominate the soul, when love intervenes it finally takes control of everything. Buonafede mocks Clarice's stubbornness but she answers back threatening him that she will find a husband for on her own if he is not capable of providing one for her. As in Mozart's Così fan tutte, the two sisters are clearly differentiated: Clarice is down to earth and her arias are full of determined pragmatism. Buonafede invites Lisetta (his daughters' maid) to share the wonders he has seen through the telescope, in an attempt to win her over. Interested on his money, she reassures him on her love for him, her fidelity and her virtues, none of which correspond to the truth. Ecclitico arrives and narrates to Buonafede that the Emperor of the Moon has invited him to his court. He will have to be transported to the moon by drinking "a certain potion". Buonafede is tempted to travel with him and, therefore, asks for some of the liquor. Ecclitico agrees and, pretending to drink half of it, gives the rest to Buonafede who drinks it, falls asleep, and dreams of flying to the Moon. Clarice and Lisetta believe at first that he is dead, then console themselves with the inheritance they will be getting.
Ecclitico's garden, decorated so as to convince Buonafede that he is on the moon
Ecclitico and Ernesto discuss the progress of their plot and when Buonafede awakens he is convinced he is on the moon. He is entertained by a ballet and clothed in elegant gowns. Ecclitico tells him the he will be joined by his daughters and servant. According to lunar custom the women will be meek. Cecco appears disguised as the Emperor of the Moon, with Ernesto as the star Hesperus. The women now arrive. Buonafede, delighted with life on the moon, is entertained by another ballet. When Lisetta enters, Buonafede tries to court her, but Cecco asks her to become Empress of the moon. Lisetta, not fully aware of the plot, is puzzled. The two daughters arrive and pay homage to the Emperor in a nonsense ceremony. Flaminia goes off with Ernesto and Clarice with Ecclitico, while Cecco prepares to crown Lisetta as Empress. In the confusion of the masquerade, Buonafede is tricked into consenting to the three marriages, in a rage only realising it is too late and he has been duped.
A room in Ecclitico's house
The conspirators, back in normal dress, have locked Buonafede in his own house - the price of his freedom will be forgiveness for his daughters and their dowries. At last he yields.
A starlit night with a full moon
Clarice and Ecclitico sing of their love. Buonafede repents of his previous strictness and there is general rejoicing and celebration.
The overture in C major is notable for its long development section and symphonic character. Re-used with reduced orchestration as the first movement of his Symphony No 63, in the opera it finishes on an open cadence. 
Throughout the opera the key of E flat is associated with the moon; the 18th century often linked the key with darkness and sleep.
Haydn in this opera moved to a new level of inspiration in the noble arias he writes for his serious characters Flaminia and Ernesto and the evocative music for the flight to the moon in Act 1.  Several numbers (vocal and instrumental) combine triple metre and a slow to moderato tempo. Flaminia’s Act I "Ragion nell’alma siede" has the typical form and coloratura of opera seria, while Lisetta’s "Se lo comanda" in Act II mixes comic and serious styles.
The ballet interludes in Act II create an imaginary world with offstage horns and bassoons and string harmonics. By contrast the G minor sinfonia which starts Act III depicts the inner rage of the duped Buonafede. 
Haydn re-used other parts of the opera in trios for flute, violin and cello (Hob IV:6-11) and Ernesto’s "Qualche volta non fa male" become the Benedictus of the Mariazeller Mass (Hob XXII:8). 
Il mondo della luna, Domenico Trimarchi, Luigi Alva, Frederica von Stade, Arleen Auger, Edith Mathis, Lucia Valentini-Terrani, Anthony Rolfe Johnson, Lausanne Chamber Orchestra and Suisse Romande Radio Chorus, conducted by Antal Doráti (Philips, 1978)
Jeff Clarke's The English Players revived the opera in 1992, and many other small opera companies have done so since. Clarke's Opera della Luna, named for the piece, presented the work at the Ilford Opera Festival in 2006.
The work is being produced in Vienna in December, 2009, conducted by Nicholas Harnoncourt and starring Vivica Genaux.
The Gotham Chamber Opera will present Il mondo della luna at the Hayden Planetarium in New York City in January of 2010, transforming the planetarium into an opera house using the 180-degree dome and projections courtesy of NASA. The production will be directed by Diane Paulus, director of Hair (musical), which received the Best Revival of a Musical at the 63rd Tony Awards.