Konzertvereinigung Wiener Staatsopernchor

Essentially identical to the Wiener Staatsopernchor, the Konzertvereinigung Wiener Staatsopernchor, or "The Concert Association of the Vienna State Opera Chorus" is the name used when performing outside the auspices of the Vienna State Opera.
From their website [edited]:
"Outside of the Vienna State Opera House the Vienna State Opera Chorus performs as the "Concert Association of the Vienna State Opera Chorus". This name expresses that the choir is not only capable of singing extended opera literature, but also a wide variety of concert repertoire. Chorus member Viktor Maiwald established the Concert Association of the Vienna State Opera Chorus in 1927, its personnel virtually identical to the Chorus of the Wiener Staatsoper, which takes part in all performances of the chorus outside the Vienna Opera House. When the Vienna State Opera Orchestra founded its own Concert ensemble (The Vienna Philharmonic - Wiener Philharmoniker), it resulted in the Vienna State Opera Chorus founding the Concert Association in 1927. The original aim has remained constant through the years: to perform the important choral works with all the great Conductors and orchestras, and to present them to the public in the highest niveau."