Question: Marta Eggerth was a singer from the silver age of which genre of light opera, "light" in terms both of music and subject matter?
Context: Gently My Songs Entreat (German: Leise flehen meine Lieder ) is a 1933 Austrian-German musical film directed by Willi Forst and starring Marta Eggerth, Luise Ullrich and Hans Jaray.  Art direction was by Julius von Borsody.  The film is a biopic of the composer Franz Schubert (1797–1828).  It was Forst's directorial debut.  A British version was made called "Unfinished Symphony".  The German title refers to the first line of the Lied "Ständchen" (Serenade) from Schubert's collection "Schwanengesang", "the most famous serenade in the world", which Eggerth performs in the film. Urban iconography is a branch of iconography, a term used both extensively, to mean a collection of illustrations of a specific subject and, within art history, the study of the subject matter of figurative representations.  Iconology is more specifically concerned with the interpretation of the same subject matter.  According to Erwin Panofsky iconography aims to identify the primary and secondary subject matter, and therefore “in doing so, iconography is an invaluable help for the establishment of dates, provenance and, occasionally, authenticity; and it furnishes the necessary basis for all further interpretation”. Operetta is a genre of light opera, "light" in terms both of music and subject matter. Philip Kraus (born November 17, 1950) is an American operatic baritone and stage director known for his performances with the Lyric Opera of Chicago, starting in 1991, and for his co-founding of Light Opera Works, a professional light opera company in Chicago, in 1980. Operetta (literally "little opera") is a genre of light opera – light in terms of the subject matter and light in terms of the music itself.  Operetta also shares many characteristics with musical theatre.  The following is a list of composers who have written works in this genre: "Magdalena" premiered at the Los Angeles Civic Light Opera on 26 July 1948, pursuant to a commission from Edwin Lester, president of that organization.  Arthur Kay conducted Irra Petina, Dorothy Sarnoff, John Raitt, Hugo Haas, Gerhard Pechner, A. Garcia, Melva Niles, Henry Reese, Ferdinand Hilt, J. Arthur, Betty Huff, Christine Matsios, Leonard Morganthaler, John Schickling, Lorraine Miller, Gene Curtsinger, Patrick Kirk, Betty Brusher, and Jack Cole (soloists).  Jules Dassin directed, Jack Cole was the choreographer, and the chorus was prepared by Robert Zeller.  Broadway veterans Howard Bay (settings and lighting) and Irene Sharaff (costumes) were also part of the creative team.  It was also presented in San Francisco at the Curran Theatre (San Francisco Light Opera) for several performances beginning August 16, 1948.  The same production opened in New York City at the Ziegfeld Theatre on September 20, 1948, and closed on December 4 after 88 performances.  Raitt, Sarnoff, and Haas reprised their roles.  No recording was made due to a strike.  "Magdalena" was revived in concert form under conductor Evans Haile on November 24, 1987, at Alice Tully Hall in New York's Lincoln Center; a recording with a slightly different cast was made in RCA's studios in 1988 and issued by CBS (later Sony) in 1989 (ASIN: B0000026QF).  The work was performed in Australia in the 1990s as part of the Opera Festival in Ballarat, Victoria, again under Haile.  More recently the Théâtre du Châtelet in Paris announced a production to open in May 2010, with Kate Whoriskey directing and Warren Adams supplying choreography. Skylight Music Theatre, known until January 2012 as Skylight Opera Theatre, is a professional light opera and musical theatre company located in Milwaukee, Wisconsin.  Founded in 1959, Skylight performs in the 358-seat Cabot Theatre at the Broadway Theatre Center in Milwaukee.  Offering a broad spectrum of works, including Gilbert and Sullivan and other light opera, small-scale operas and musicals, the company is known for its all-English repertoire. The Los Angeles Civic Light Opera (LACLO) was an American theatre/opera company in Los Angeles, California.  Founded under the motto "Light Opera in the Grand Opera manner" in 1938 by impresario Edwin Lester, the organization presented fifty seasons of theatre before closing due to financial reasons in 1987.  Typically the LACLO presented four to six productions during an annual season.  The company produced or co-produced several of their own shows in addition to bringing in shows from Broadway to California, often with their original casts.  Productions that originated at the LACLO and then went on to wider success, included "Song of Norway" (1944), "Magdalena" (1948), "Kismet" (1953), "Peter Pan" (1954) and "Gigi" (1973).  Initially the organization mainly presented American operettas, but by the 1960s the company was presenting mostly musical theatre; although the company never completely left its roots. The Divine Spark is a 1935 British musical film directed by Carmine Gallone and starring Marta Eggerth, Phillips Holmes, Benita Hume and Donald Calthrop.  An Italian-language version "Casta Diva" was shot simultaneously.  Both films were made at the Tirrenia Studios in Italy. Marta Eggerth (17 April 1912 – 26 December 2013) was a Hungarian-born American actress and singer from "The Silver Age of Operetta".  Many of the 20th century's most famous operetta composers, including Franz Lehár, Fritz Kreisler, Robert Stolz, Oscar Straus and Paul Abraham, composed works especially for her.
Answer: Operetta