Within four years, three German musicians wrote down how to play their instruments. Johann Joachim Quantz published his method for the flute in Berlin in 1752. Carl Philipp Emanuel Bach published his Versuch über die wahre Art das Clavier zu spielen, Essay on the True Art of Playing Keyboard Instruments, in Berlin in 1753. Leopold Mozart published his Versuch einer gründlichen Violinschule, a thorough violin method, in Augsburg in 1756. In 1829 the composer Carl Friedrich Zelter wrote that Mozart’s method could be used solange die Violine eine Violine bleibt, as long as the violin remains a violin. Together, the three books are today the most important source on how music was performed in the middle of the 18th century.