Рудольф II
The original documents of 1581 indicate the composer only as "Sieur de Beaulieu". The error concerning his name, and consequent separation of the bass singer and composer into two biographies, is due to an erroneous "Lambert de Beaulieu" in a letter by Rudolf II, Holy Roman Emperor to the French king attempting to employ the composer Beaulieu for his own court. The error in Rudolf's letter was reproduced by François-Joseph Fétis in his influential "Biographie universelle des musiciens".