The Vienna State Opera Chorus is generally ranked among the finest choral ensembles in the world. The VSOC consists of 92 members divided evenly among male and female singers. The chorus is structured as follows: for female singers there are 15 first sopranos, 10 second, 10 first altos, and 11 second; for male singers there are 12 first tenors; 11 second, 11 first basses, and 12 second. The VSOC perform most nights of the week from September 1 to June 30, owing to the busy opera schedule of the Vienna State Opera, which stages over 50 opera productions and 200 performances yearly. Despite these taxing demands, the chorus often performs at orchestral and choral concerts, makes occasional tours abroad, and appears on recordings. When performing away from the opera house, the VSOC sings under the name of the Concert Association of the Vienna State Opera Chorus. Still, on recordings of non-operatic fare, the ensemble is usually listed as the Vienna State Opera Chorus. The VSOC has appeared on more than 400 recordings, spread over virtually every major and many minor labels.
The Vienna State Opera Chorus was founded in 1869, the year the construction of the Vienna Opera Court Building was finished. From 1923 the VSOC began making regular appearances at the Salzburg Festival.
In 1927 the VSOC, led by one of its members, Viktor Maiwald, created its non-operatic branch, the Concert Association of the Vienna State Opera Chorus. In the ensuing years, a small schedule of concerts was arranged for the ensemble. Also, from 1927, the VSOC members began electing their own concert director. That individual is often the music director of the Vienna State Opera, as with Seiji Ozawa (2002-2010), who also serves as conductor of the Vienna State Opera Orchestra. Bruno Walter (1936-1938), Karl Böhm (1954-1981), and Claudio Abbado (1987-2002) have been other illustrious past conductors of the VSOC.
In 1956 newly appointed music director of the Vienna State Opera, Herbert von Karajan, changed the German-language performance policy of the Vienna State Opera, declaring that all operas must thenceforth be sung in their original language. The VSOC, with much to relearn, smoothly made the abrupt transition. The VSOC continues to maintain its extremely busy schedule: at the 2008 Salzburg Festival the VSOC sang in six operas and four concert works, and its 2009 concert schedule included appearances in May in Taiwan and in November in South Korea.