Background: The Vienna Boys' Choir (German: Wiener Sangerknaben) or Vienna Choir Boys is a choir of boy sopranos and altos based in Vienna, Austria. It is one of the best known boys' choirs in the world. The boys are selected mainly from Austria, but also from many other countries. The choir is a private, not-for-profit organization.
Context: The choir is the modern-day descendant of the boys' choirs of the Viennese Court, dating back to the late Middle Ages. The choir was, for practical purposes, established by a letter from Emperor Maximilian I of Habsburg on 30 June 1498, instructing court officials to employ a singing master, two basses and six boys. Jurij Slatkonja became the director of the ensemble. The role of the choir (numbering between 24 and 26) was to provide musical accompaniment for the church mass. Additionally, the Haydn brothers were members of the St. Stephen's Cathedral choir, directed at the time by Georg Reutter II, who used this choir in his duties for the imperial court, which at the time had no boy choristers of its own.  Over the centuries, the choir has worked with many composers, including Heinrich Isaac, Hofhaimer, Biber, Fux, Caldara, Gluck, Salieri, Mozart, Franz Schubert and Bruckner.  In 1920, following the fall of the Austrian Empire, the Hofkapelle (court orchestra) was disbanded. However, the rector at the time, Josef Schnitt, sought a continuation of the tradition. In 1924, the Vienna Boys' Choir was officially founded, and it has evolved into a professional music group. The choir adopted the now-famous blue and white sailor suit, replacing the imperial military cadet uniform that included a dagger. The composer HK Gruber is one of the graduates of the reformed choir.  Since 1948, the Palais Augarten has served as their rehearsal venue and boarding school, which goes from kindergarten level up to middle school level.  In 1961, Walt Disney filmed Almost Angels, a fictional drama about (and starring) the Vienna Boys' Choir, set and filmed in the Palais Augarten. It was Disney who, for cinematographic reasons, persuaded the Austrian government to allow the boys to legally wear the Austrian national emblem on the breast of their uniform, a tradition that continues to this day.
Question: Where did they sing?
Answer: The role of the choir (numbering between 24 and 26) was to provide musical accompaniment for the church mass.

Background: Vlachs (English:  or , or rarely ) is a historical term and exonym used for the Eastern Romance-speaking peoples especially in the Balkans. The term also became a synonym in the Balkans for the social category of shepherds, and was also used for non-Romance-speaking peoples, in recent times in the western Balkans derogatively. Apart from the Romanians and Moldovans, there are indigenous Romance-speaking groups in Greece, Albania and Macedonia, such as the Aromanians and Megleno-Romanians. "Vlachs" were initially identified and described during the 11th century by George Kedrenos.
Context: The word "Vlach" is etymologically derived from the ethnonym of a Celtic tribe, adopted into Proto-Germanic *Walhaz which meant "stranger", from *Wolka- (Caesar's Latin: Volcae, Strabo and Ptolemy's Greek: Ouolkai).  Via Latin, in Gothic, as *walhs, the ethnonym took on the meaning "foreigner" or "Romance-speaker", and was adopted into Greek Vlahi (Blakhoi), Slavic Vlah, Hungarian olah and olasz, etc. The root word was notably adopted in Germanic for Wales and Walloon (German: Welsch), and in Poland Wlochy became an exonym for Italians. Via both Germanic and Latin, the term started to signify "stranger, foreigner" also in the Balkans, where it in its early form was used for Romance-speakers, but the term eventually took on the meaning of "shepherd, nomad". The Romance-speaking communities themselves however used the endonym (they called themselves) "Romans". During the early history of the Ottoman Empire in the Balkans, there was a social class of Vlachs in Serbia and Macedonia, made up of Christians who served as auxiliary forces and had the same rights as Muslims. In Croatia, the term became derogatory, and Vlasi was used for the ethnic Serb community.  Romanian scholars have suggested that the term Vlach appeared for the first time in the Eastern Roman Empire and was subsequently spread to the Germanic- and then Slavic-speaking worlds through the Norsemen (possibly by Varangians), who were in trade and military contact with Byzantium during the early Middle Ages (see also Blakumen).  The term "Vlach" is used in scholarship for the Romance-speaking communities in the Balkans, especially those in Greece, Albania and Macedonia.
Question: What are the circumstances of the origin of the Vlachs?
Answer:
The word "Vlach" is etymologically derived from the ethnonym of a Celtic tribe, adopted into Proto-Germanic *Walhaz which meant "stranger", from *Wolka