Das verratene Meer ("The Betrayed Sea") is an opera in two parts and 14 scenes, with music by Hans Werner Henze to a German libretto by Hans-Ulrich Treichel, after Yukio Mishima's novel "The Sailor Who Fell from Grace with the Sea".
 Composed between 1986 and 1989, it was Henze's 9th opera, his third that he wrote for the Deutsche Oper in Berlin.
L'Upupa und der Triumph der Sohnesliebe (English: "The Hoopoe and the Triumph of Filial Love") is an opera by Hans Werner Henze with a German libretto by the composer, inspired by Arab and Persian legends.
 This is Henze's 15th, and self-stated final, opera, and the first where he has written his own libretto.
Hans Werner Henze's Symphony No. 1 was premiered in Darmstadt in 1947.
 The premiere was hit by Henze’s accustomed bad luck.
 The orchestral parts, handwritten by the composer himself, had become illegible during photocopying in Schott’s offices and despite the young composer’s best efforts to ink in the parts throughout the night, only the slow movement was performed.
 The whole symphony was eventually premiered a year later, although Henze himself conducted the work only after comprehensive revision.
Ondine is a ballet in three acts created by the choreographer Sir Frederick Ashton and composer Hans Werner Henze.
 Ashton originally produced Ondine for the Royal Ballet in 1958, with Henze commissioned to produce the original score, published as "Undine", which has since been restaged by other choreographers.
 The ballet was adapted from a novella called "Undine" by Friedrich de la Motte Fouqué and it tells the tale of a water nymph who is the object of desire of a young prince named Palemon.
 The première of the ballet took place at the Royal Opera House, London, on 27 October 1958, with the composer as guest conductor.
 The first major revival of this Ashton/Henze production took place in 1988.
George Jacob Gershwin ( ; September 26, 1898 July 11, 1937) was an American composer and pianist.
 Gershwin's compositions spanned both popular and classical genres, and his most popular melodies are widely known.
 Among his best-known works are the orchestral compositions "Rhapsody in Blue" (1924) and "An American in Paris" (1928) as well as the opera "Porgy and Bess" (1935).
We Come to the River – Wir erreichen den Fluss is an opera by Hans Werner Henze to an English-language libretto by Edward Bond.
 Henze and Bond described this work as "Actions for music", rather than an opera.
 It was Henze's 7th opera, written originally for the The Royal Opera in London, and takes as its focus the horrors of war.
 The opera was first performed at the Royal Opera House, Covent Garden, London on 12 July 1976, with the composer as producer, Jürgen Henze as director, and David Atherton conducting.
 It was subsequently staged at the Deutsche Oper Berlin, and received its first American performance at Santa Fe Opera in 1984, conducted by Dennis Russell Davies.
The WDR Symphony Orchestra Cologne (WDR Sinfonieorchester Köln) is a German orchestra based in Cologne.
 The orchestra was founded in 1947 by Allied occupation authorities after World War II, as the orchestra of "Nordwestdeutscher Rundfunk" (NWDR; Northwest German Radio).
 The orchestra was named "Kölner Rundfunk-Sinfonie-Orchester" (Cologne Radio Symphony Orchestra) and from the 1990s "WDR Symphony Orchestra".
 The orchestra is particularly known for its performances of 20th-century and contemporary music.
 It has commissioned and premiered works from such composers as Luciano Berio, Hans Werner Henze, Mauricio Kagel, Krzysztof Penderecki, Karlheinz Stockhausen and Bernd Alois Zimmermann.
Hans Werner Henze composed the nine Sacred Concertos that comprise his Requiem over the course of three years from 1991 to 1993 on commissions from the London Sinfonietta, Suntory Corporation for the NHK Philharmonic, and Westdeutscher Rundfunk, Cologne.
 The first movement, "Introitus: Requiem Aeternam" was commissioned by the London Sinfonietta as part of a memorial concert for Artistic Director Michael Vyner who died on 20 October 1989.
 In addition to Henze, the London Sinfonietta also commissioned seven other prominent composers (Luciano Berio, Sir Harrison Birtwistle, Sir Peter Maxwell Davies, Toru Takemitsu, Oliver Knussen, and Nigel Osborne) to write works in Vyner's memory to make up the program which was performed on the 6 May 1990.
Boulevard Solitude is a "Lyrisches Drama " (lyric drama) or opera in one act by Hans Werner Henze to a German libretto by Grete Weil after the play by Walter Jockisch, in its turn a modern retelling of François Prévost's "Manon Lescaut".
 The piece is a reworking of the Manon Lescaut story, already adapted operatically by Auber, Massenet and Puccini, and here relocated to Paris after the Second World War where, as is noted in Grove, the focus of the story moves away from Manon and towards Armand des Grieux.
 It became Henze’s first fully-fledged opera.
 The work stands out for its strong jazz influences, from a composer who had hitherto been associated with twelve tone technique.
Hans Werner Henze (1 July 1926 – 27 October 2012) was a German composer.
 His large oeuvre of works is extremely varied in style, having been influenced by serialism, atonality, Stravinsky, Italian music, Arabic music and jazz, as well as traditional schools of German composition.
 In particular, his stage works reflect "his consistent cultivation of music for the theatre throughout his life".

Question: Hans Werner Henze and George Gershwin, had which musical occupation?
Answer: composer