Question: Cendrillon, a three act operetta, premiered on the 23rd of April in this typical Paris setting.

Context paragraphs:
Le testament de la tante Caroline: Le testament de la tante Caroline ("Aunt Caroline's Will") is an opéra bouffe or operetta by composer Albert Roussel and librettist Nino (pseudonym of Michel Veber).  The original production was in the Czech language (prepared by Julie Reisserová) and in three acts, but the work was later revised into a one act operetta in the French language.  The operetta tells the story of a family who is caught in a difficult set of circumstances surrounding the contents of a will and the dispersal of a vast fortune.  The work premiered in Olomouc on 14 November 1936.

Salon (gathering): A salon is a gathering of people under the roof of an inspiring host, held partly to amuse one another and partly to refine the taste and increase the knowledge of the participants through conversation.  These gatherings often consciously followed Horace's definition of the aims of poetry, "either to please or to educate" ("aut delectare aut prodesse").  Salons, commonly associated with French literary and philosophical movements of the 17th and 18th centuries, were carried on until as recently as the 1940s in urban settings.

LATTC/Ortho Institute station: LATTC/Ortho Institute, officially Los Angeles Trade-Technical College/Orthopaedic Institute for Children (formerly 23rd Street), is an at-grade light rail station in the Los Angeles County Metro Rail system, located on Flower Street at 23rd Street, in the North University Park neighborhood of Los Angeles.  This station is served by the Expo Line.  It is also served by the Metro Silver Line.  Northbound Silver Line buses to Downtown Los Angeles stop at Figueroa St./23rd Street.  Southbound Silver Line buses to Harbor Gateway Transit Center/Pacific/21st Street stop at Flower St./ 23rd Street.

Three Act Tragedy: Three Act Tragedy is a work of detective fiction by Agatha Christie first published in the United States by Dodd, Mead and Company in 1934 under the title Murder in Three Acts and in the UK by the Collins Crime Club in January 1935 under Christie's original title.  The US edition retailed at $2.00 and the UK edition at seven shillings and sixpence (7/6).

Gustavo primo, re di Svezia: Gustavo primo, re di Svezia ("Gustavus the First, King of Sweden") is a three act opera seria by Baldassare Galuppi, with a libretto by Carlo Goldoni, fictionalising events in the life of Gustav I of Sweden.  Composed in honour of the Genoese nobleman marchese Giovanni Giacomo Grimaldi, it premiered on 25 May 1740 at Venice's Teatro San Samuele.  It was first recorded in 2003 by Karoly, Gonzalez, Cecchetti and the Capella Savaria Baroque Orchestra, conducted by Fabio Pirona.

Members of the 23rd Seanad: This is a list of the members of the 23rd Seanad Éireann, the upper house of the Oireachtas (legislature) of Ireland.  These Senators were elected from 24 July 2007 onwards after postal voting closed.  The Taoiseach's nominees were announced on 3 August 2007.  The Seanad election took place after the 2007 general election for the Dáil.  The term of the 23rd Seanad was from 24 July 2007 to 25 April 2011.  The 23rd Seanad first met at Leinster House on 13 September 2007.  Pat Moylan was elected as the new Cathaoirleach of the Seanad.

N'écoutez pas, mesdames !: N'écoutez pas, mesdames !  is a three act comedy by Sacha Guitry, premiered at théâtre de la Madeleine on 23rd May 1942.

Maritana: 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.

Cendrillon (Viardot): Cendrillon is a chamber operetta with dialogue in three acts by Pauline Viardot based on the story of "Cinderella".  The work, for a cast of seven with piano orchestration, premiered in Viardot's Paris salon on 23 April 1904, when she was 83, and was published later that year.  Historians are unsure of when the opera was actually composed, although it is thought to be after the death of Viardot's friend (and possibly her lover) Ivan Turgenev in 1883 as he did not write the libretto.  It has been described as "a retelling of the Cinderella story with Gallic wit, Italianate bel canto, and a quirkiness all her [Viardot's] own."

23rd Indian Infantry Brigade: The 23rd Indian Infantry Brigade was an infantry brigade formation of the Indian Army during World War II from 1941 to at least 1947.  The brigade was formed in February 1941, at Loralai in India and in June 1941, assigned to the 14th Indian Infantry Division.  In March 1942, the brigade was reassigned to the 23rd Indian Infantry Division, just before being renumbered 123rd Indian Infantry Brigade.  As the 123rd the brigade served in the Burma Campaign with not only the 23rd but with the 14th again and the 5th Indian Infantry Division.

Supporting paragraphs: Cendrillon (Viardot) Salon (gathering)
Answer: Salons