Question: The Konzertstück in F minor for Piano and Orchestra, Op. 79, J. 282, was written by Carl Maria von Weber, and he started work on it in 1815, and completed it on the morning of the premiere of which opera, with spoken dialogue in three acts?
Context: Oberon, or The Elf King's Oath is a 3-act romantic opera in English with spoken dialogue and music by Carl Maria von Weber.  The libretto by James Robinson Planche was based on a German poem, "Oberon", by Christoph Martin Wieland, which itself was based on the epic romance "Huon de Bordeaux", a French medieval tale. The "Carl Maria von Weber" College of Music (Hochschule für Musik "Carl Maria von Weber" in German, and also/formerly known as Dresden Conservatory or Dresden Royal Conservatory) is a college of music in Dresden, Germany. The Grand Duo Concertant, Opus 48, J204, is a three-movement work for clarinet and piano composed by Carl Maria von Weber from 1815 to 1816.  It is a virtuosic piece for both instruments.  Weber most likely composed the work for himself (on piano) and his friend Heinrich Baermann, a leading clarinettist of the era, although it has also been suggested that the intended clarinettist was Johann Simon Hermstedt. Der Freischütz , Op. 77, J. 277, (usually translated as "The Marksman" or "The Freeshooter") is a German opera with spoken dialogue in three acts by Carl Maria von Weber with a libretto by Friedrich Kind.  It premiered on 18 June 1821 at the Schauspielhaus Berlin.  It is considered the first important German Romantic opera, especially in its national identity and stark emotionality. Carl Maria von Weber wrote his Clarinet Concerto No. 1 in F minor, Op. 73 (J. 114) for the clarinettist Heinrich Bärmann in 1811.  The piece is considered a gem in the instrument's repertoire.  It is written for clarinet in B♭.  The work consists of three movements in the form of fast, slow, fast. Abu Hassan is a comic opera in one act by Carl Maria von Weber to a German libretto by , based on a story in "One Thousand and One Nights".  It was composed between 11 August 1810 and 12 January 1811 and has set numbers with recitative and spoken dialogue.  The work is a Singspiel in the then popular Turkish style. Peter Schmoll und seine Nachbarn ("Peter Schmoll and his Neighbours") is the third opera by Carl Maria von Weber and the first for which the music has survived, though the libretto has not.  It was written in 1802 when the composer was only 15 and premiered in Augsburg the following year.  The opera takes the form of a Singspiel, mixing spoken dialogue and musical numbers.  The libretto is based on a novel by C.G. Cramer. Carl Maria von Weber's Concerto for Bassoon in F Major, Op. 75 (J. 127) was composed in 1811 for Munich court musician Georg Friedrich Brandt, and then revised in 1822.  Primarily an opera conductor and composer, Weber had only arrived a few months earlier in Munich, where he was extremely well received.  The concerto is one of two pieces written for bassoon by Weber, the other being "Andante e Rondo Ungarese", Op. 35 (J. 158).  A typical performance lasts 18–20 minutes. The Konzertstück in F minor for Piano and Orchestra, Op. 79, J. 282, was written by Carl Maria von Weber.  He started work on it in 1815, and completed it on the morning of the premiere of his opera "Der Freischütz", 18 June 1821.  He premiered it a week later, on 25 June, at his farewell Berlin concert. The Concertino for Horn and Orchestra in E minor, J188 (Op.  45), was composed in 1815 by Carl Maria von Weber.  It is an extremely taxing work, whether played on the natural horn for which it was written, or on the modern valve horn.  The soloist is accompanied by a small orchestra.  It requires, among other feats, that the player produce what is in effect a four-note chord using the interplay between humming and the sound from the instrument, a technique known as multiphonics.
Answer: Der Freischütz