Basically, they’ve been the best in the business for last 516 years. In 1498, Holy Roman Emperor Maximilian I moved his court to Vienna in what is now Austria. He decreed that six singing boys join his official musicians and ordered the court to find the best young talent from around his realm, which included present day Germany, Holland, and Italy. Since then, what is now called the “Vienna Boys’ Choir” has been astounding the world with an angelical sound, enthralling harmonies, and expansive repertoire. This weekend, choir members will perform in Queens, thanks to the Kupferberg Center for the Arts.