Question: Rotraud Hansmann was a singer in the recordings by which Austrian conductor, particularly known for his historically informed performances of music from the Classical era and earlier?
Context: Aachener Bachverein (often abbreviated as ABV) is a German oratorio choir of the Evangelical Church in the Rhineland in the city of Aachen that was founded in 1913 by Heinrich Boell.  Although the chorus sings a varied repertoire that encompasses music from all historical periods to new compositions, the ensemble is particularly known for their historically informed performances of baroque and classical period music that are often made in conjunction with internationally renowned instrumental ensembles and orchestras.  The choir frequently tours, has had several of their performances broadcast on German radio, and has recorded a number of cantatas by J.S. Bach. Andrew Parrott (born 10 March 1947) is a British conductor, perhaps best known for his pioneering "historically informed performances" of pre-classical music.  He conducts a wide range of repertoire, including contemporary music.  He conducted the premiere of Judith Weir's "A Night at the Chinese Opera" (as well as its first recording).  He has also recorded new music by other modern British composers (including John Tavener), and by Vladimír Godár. Daniel E. Abraham (born 1968) is an American conductor and musicologist.  He studied conducting under Paul Traver at the University of Maryland and William Weinert at the Eastman School of Music.  In 1997 he was a Conducting Fellow at the Oregon Bach Festival, where he studied under Helmuth Rilling.  He has also studied privately with David Hoose of Boston University.  In 1996 he was the recipient of the Irving Lowens Award for excellence in student musicological research and in 1998 he received the Daniel Pomeroy Prize from the American Handel Society, for Performance and Scholarship in Eighteenth-Century Music.  He is currently the Director of Choral Activities at American University and the director of "The Bach Sinfonia", the latter of which he founded in 1995.  Known for both his research and knowledge in the area of early music and the music of the baroque period, Abraham's has written several publications on the topic of historically informed performances. Early music is music, especially Western art music, composed prior to the Classical era.  The term generally comprises Medieval music (500–1400) and Renaissance music (1400–1600), but can also include Baroque music (1600–1760), and, according to some authorities such as Kennedy (who excludes Baroque), Ancient music (before 500 AD).  According to the UK's National Centre for Early Music, the term "early music" refers to both a repertory (European music written between 1250 and 1750 embracing Medieval, Renaissance and the Baroque) – and a historically informed approach to the performance of that music.  However, today this term has come to include "any music for which a historically appropriate style of performance must be reconstructed on the basis of surviving scores, treatises, instruments and other contemporary evidence." Nikolaus Harnoncourt (Johann Nikolaus Graf [Count] de la Fontaine und d’Harnoncourt-Unverzagt; 6 December 1929 – 5 March 2016) was an Austrian conductor, particularly known for his historically informed performances of music from the Classical era and earlier.  Starting out as a classical cellist, he founded his own period instrument ensemble, Concentus Musicus Wien, in the 1950s, and became a pioneer of the Early Music movement.  Around 1970, Harnoncourt started to conduct opera and concert performances, soon leading renowned international symphony orchestras, and appearing at leading concert halls, operatic venues and festivals.  His repertoire then widened to include composers of the 19th and 20th centuries.  In 2001 and 2003, he conducted the Vienna New Year's Concert.  Harnoncourt was also the author of several books, mostly on subjects of performance history and musical aesthetics. The listing shows recordings of the Mass in B minor, BWV 232, by Johann Sebastian Bach.  The selection is taken from the 237 recordings listed on bach-cantatas as of 2015, beginning with the first recording by a symphony orchestra and choir to match, conducted by Albert Coates.  Beginning in the late 1960s, historically informed performances paved the way for recordings with smaller groups, boys choirs and ensembles playing period instruments, and eventually to recordings using the one-voice-on-a-vocal-part scoring first argued for by Joshua Rifkin in 1982. Rotraud Hansmann (born 1 March 1940) is an Austrian soprano in opera and concert.  She was a singer in the recordings by Nikolaus Harnoncourt which began historically informed performances, such as Monteverdi's operas and works by Johann Sebastian Bach.  She was a teacher at the University of Music and Performing Arts, Vienna. Frieder Bernius (born 22 June 1947) is a German conductor, the founder and director of the chamber choir Kammerchor Stuttgart, founded in 1968.  They became leaders for historically informed performances.  He founded the Stuttgart festival of Baroque music, "Internationale Festtage Alter Musik", in 1987, and is a recipient of the Edison Award (1990), Diapason d'Or (1990) and the Order of Merit of the Federal Republic of Germany (1993). Gary Cooper is an English conductor and classical keyboardist who specialises in the harpsichord and fortepiano.  He is known as an interpreter of the keyboard music of Bach and Mozart, and as a conductor of historically informed performances of music from the Renaissance, Baroque, Classical and Romantic periods. The Innsbruck Festival of Early Music (German: Innsbrucker Festwochen der Alten Musik) is a festival of historically informed performances of music from the late Renaissance, Baroque and early Classical periods which takes place annually in Innsbruck, Austria.  It was founded in 1976.
Answer: Nikolaus Harnoncourt