The Wiener Sängerknaben or Vienna Boys' Choir is the world's foremost children's choral group. It is among the oldest of all musical organizations, having been founded on July 7, 1498. Today, there are 100 choristers between the ages of nine and fourteen, divided into four touring choirs. Each Choir spends nine to eleven weeks of the academic year on tour. Together, the choirs give around 300 concerts each year, attended by almost half a million spectators worldwide. Over the centuries, illustrious composers have written masterpieces for the Boys' Choir of the Imperial Chapel, including Mozart, Bruckner, Gluck, and Schubert. Many great musicians got their start as members of the Boys' Choir; among them were the great conductors Hans Richter, Clemens Krauss, and Lovro von Matacic. In 1498, the Roman Emperor Maximilian I wished boys' voices to be added to the Choir of the Imperial Chapel or Hofkapelle, thus established a tradition of having the boys sing in weekly Sunday masses in the Imperial Chapel of the Hofburg Palace in Vienna, a practice that continues today. The Choir has a long history and tradition that has been educating children for more than 500 years.