Vienna's Arnold Schoenberg Choir performs music from the Renaissance to the contemporary era, including, at times, that of its namesake, but it has pursued a special focus on Baroque music. The choir also participates in operatic productions and since 2006 has been the opera chorus in residence at the Theater an der Wien. The choir often collaborated with historical performance specialist Nikolaus Harnoncourt and his Concentus Musicus Wien. Harnoncourt led the group in two of its earliest recordings, one of Mozart's Requiem in D minor, K. 626, and one of Handel's oratorio Samson, HWV 57. Notable recordings include a complete seven-volume set of Schubert's rarely heard secular choral music. In 2016, the choir participated in Harnoncourt's final recording, Beethoven's Missa Solemnis. The Arnold Schoenberg Choir returned to the recording scene that year on a recording of Erwin Schulhoff's opera Flammen.