Question: Oszkár Kálmán was the first lead of a one act opera by which composer?

Context articles: Madeline Lee
Bluebeard's Castle
Oszkár Kálmán
Letters, Riddles and Writs
Gallantry (opera)
Bianca (opera)
Von heute auf morgen
Sapho (Gounod)
Maritana
Safié

Madeline Lee is a one act opera, composed by John Haddock to a libretto written jointly by the composer and Michael Campbell.
 It premiered at the Sydney Opera House on 8 October 2004 in an Opera Australia production directed by Michael Campbell and conducted by Tom Woods.
Bluebeard's Castle (Hungarian: A kékszakállú herceg vára ; literally: "The Blue-Bearded Duke's Castle") is a one-act opera by Hungarian composer Béla Bartók.
 The libretto was written by Béla Balázs, a poet and friend of the composer, and is written in Hungarian, based on the French literary tale "La Barbe bleue" by Charles Perrault.
 The opera lasts only a little over an hour and there are only two singing characters onstage: Bluebeard ("Kékszakállú "), and his new wife Judith ("Judit " ); the two have just eloped and Judith is coming home to Bluebeard's castle for the first time.
Oszkár Kálmán (19 June 1887 - 17 September 1971) was a Hungarian bass, remembered as the first Bluebeard.
 He was born in Kisszentpéter (in present day Romania) and in 1913 made his debut as Sarastro at the Royal Opera House in Budapest,
Letters, Riddles and Writs is a one act opera for television by Michael Nyman.
 The story is devised by Nyman, with a libretto by Jeremy Newson and Pat Gavin that incorporates Emily Anderson's English translations of correspondence and other texts by Wolfgang Amadeus Mozart, the subject of the opera.
Gallantry is a one act opera by composer Douglas Moore.
 The work is a parody of soap opera, complete with sung commercial interruptions.
 The work uses an English language libretto by Arnold Sundgaard.
 The opera premiered in a double bill with Dominick Argento's "The Boor" on March 19, 1958, in New York City at the now-destroyed Brander Matthews Theater on 117th Street, between Amsterdam Avenue and Morningside Drive.
 It was presented by the Columbia University School of Music with a student cast.
 It has subsequently been staged by several other university opera theatre programs in the United States and Canada, including UCLA (1958, 1974, and 1994), Immaculate Heart College (1968), Goucher College (1969), the University of Michigan (1978), the University of Toronto (1988), San Diego State University (1989), Pepperdine University (1990), Wilfrid Laurier University (1992), the University of Arizona (1995), George Washington University (1999), and the University of Wisconsin (2003) among others.
 The University of Southern California toured the opera to the Netherlands in 1968.
Bianca is a one act opera by American composer Henry Kimball Hadley.
 The opera's libretto was an English-language adaptation of Carlo Goldoni's comedy "The Mistress of the Inn" by Grant Stewart.
 Hadley finished the score in January, 1917, and entered it in a competition for the best American opera without chorus, for which William Wade Hinshaw offered a $1000 prize and a promise to produce the opera in New York City by the American Society of Singers.
 It won, and was produced on October 19, 1918, at the Park Theater in Manhattan, with the composer conducting, and soprano Maggie Teyte in the title role.
Von heute auf morgen ("From Today to Tomorrow" or "From One Day to the Next") is a one act opera composed by Arnold Schoenberg, to a German libretto by "Max Blonda", the pseudonym of Gertrud Schoenberg, the composer's wife.
 It is the composer's opus 32.
Sapho is a 3-act opera by Charles Gounod to a libretto by Émile Augier which was premiered by the Paris Opera at the Salle Le Peletier on 16 April 1851.
 It was presented only 9 times in its initial production, but was a "succès d'estime" for the young composer, with the critics praising Act 3 in particular.
 It was later revived in 2-act (1858) and 4-act (1884) versions, achieving a total of 48 performances.
Maritana is a three act opera including both spoken dialogue and some recitatives, composed by William Vincent Wallace, with a libretto by Edward Fitzball (1792–1873).
 The opera is based on the 1844 French play "Don César de Bazan" by Adolphe d'Ennery and Philippe François Pinel Dumanoir, which was also the source material for Jules Massenet's opéra comique "Don César de Bazan" (the character of Don César de Bazan first appeared in Victor Hugo's "Ruy Blas").
 The opera premiered at the Theatre Royal, Drury Lane on 15 November 1845.
Safié is a one act opera by American composer Henry Kimball Hadley.
 The opera's libretto was written in English by Edward Oxenford, but its premiere, on April 4, 1909 in Mainz, Germany, was given in a German translation by Otto Neitzel.
 Hadley conducted the premiere, and the title role was sung by American soprano Marguerite Lemon.