Question: Die Soldaten and Nixon in China, are which type of performance?

Context paragraphs:
Shumi Maritsa: "Shumi Maritsa" (Bulgarian: Шуми Марица ] ) was the Bulgarian national anthem from 1886 until 1944.  The music was derived from the German folk song "Wenn die Soldaten durch die Stadt marschieren" that was very popular in Bulgaria in the mid-19th century.  The original text was written by Nikola Zhivkov, a head teacher in Veles (now in the Republic of Macedonia).  The lyrics were edited many times, most notably in 1912 by the poet Ivan Vazov.

Michael Gielen: Michael Andreas Gielen (born 20 July 1927) is an Austrian conductor and composer.  He promoted contemporary music in opera and concert, conducting premieres such as György Ligeti's "Requièm", Karlheinz Stockhausen's "Carré" and Bernd Alois Zimmermann's opera "Die Soldaten".  He directed the Frankfurt Opera from 1977 to 1987, later called the Gielen Era, winning stage directors such as Hans Neuenfels and Ruth Berghaus, and reviving operas such as Schreker's "Die Gezeichneten" which had premiered in Frankfurt in 1918.

Soldaten (Gurlitt): Soldaten is a 1930 opera in 3 acts by Manfred Gurlitt after the play of Jakob Michael Reinhold Lenz.  It was premiered 9 November 1930, Düsseldorf, but later overshadowed by Bernd Alois Zimmermann's setting of "Die Soldaten" (1965).

Nixon in China: Nixon in China is an opera in three acts by John Adams, with a libretto by Alice Goodman.  Adams' first opera, it was inspired by U.S. President Richard Nixon's visit to China in 1972.  The work premiered at the Houston Grand Opera on October 22, 1987, in a production by Peter Sellars with choreography by Mark Morris.  When Sellars approached Adams with the idea for the opera in 1985, Adams was initially reluctant, but eventually decided that the work could be a study in how myths come to be, and accepted the project.  Goodman's libretto was the result of considerable research into Nixon's visit, though she disregarded most sources published after the 1972 trip.

Ranks of the German Bundeswehr: The Ranks of the German Armed Forces, (in German: Bundeswehr), were set up by the President with the "Anordnung des Bundespräsidenten über die Dienstgradbezeichnungen und die Uniform der Soldaten" on the basis of section 4, paragraph 3 of the "Soldatengesetz" (federal law concerning the legal status of soldiers).  The "Bundesbesoldungsordnung" (Federal Salary Scale Regulation) regulates the salary scales of all Federal office holders and employees including soldiers.  The 'ZdV-64/10 - Abkürzungen in der Bundeswehr' gives the abbreviations and a list of the abbreviations.

Nixon goes to China: The phrase "Nixon goes to China", "Nixon to China", or "Nixon in China" is a historical reference to United States President Richard Nixon's 1972 visit to the People's Republic of China, where he met with Chairman Mao Zedong.  The metaphor is often expressed as the observation "Only Nixon could go to China" or "It took Nixon to go to China".

Die Soldaten: Die Soldaten ("The Soldiers") is a four-act opera in German by Bernd Alois Zimmermann, based on the 1776 play by Jakob Michael Reinhold Lenz.  Written and revised in phases between 1957 and 1964, it was premiered in 1965 and dedicated to Hans Rosbaud.  Zimmermann himself faithfully adapted the play into the libretto, the only changes to the text being repeats and small cuts.  It is the composer's only completed opera and is considered an important work of the second half of the 20th century.

The Soldiers (play): The Soldiers (German: Die Soldaten) is a 1776 comedy by Jakob Michael Reinhold Lenz written from his own experiences during his service under Friedrich Graf Kleist von Nollendorf.  It was influential on Georg Büchner in his attempt to write the drama "Woyzeck" (left incomplete 1837), although that is set at a lower social strata.  The play is the source of two operas "Soldaten" by Manfred Gurlitt (1930) and "Die Soldaten" by Bernd Alois Zimmermann (1965).

Claudia Barainsky: Claudia Barainsky (born 30 September 1965) is a German operatic soprano.  She has performed internationally, and won awards for her roles in contemporary operas such as Bernd Alois Zimmermann's "Die Soldaten" and Aribert Reimann's "Medea".

Bernd Alois Zimmermann: Bernd Alois Zimmermann (20 March 1918, Bliesheim, Rhine Province – 10 August 1970, Königsdorf (Frechen); full name "Bernhard Alois Zimmermann") was a West German composer.  He is perhaps best known for his opera "Die Soldaten", which is regarded as one of the most important German operas of the 20th century, after those of Berg.  As a result of his individual style, it is hard to label his music as avant-garde, serial or postmodern.  His music employs a wide range of methods including the twelve-tone row and musical quotation.

Supporting paragraphs: Die Soldaten Nixon in China
Answer: opera