During the long, rather dark and cold winter semester, it is always pleasant to look forward to the music which is traditionally played in Germany at Christmas. In the winter semester of 2005 - 6, I had two different lectures on "Elementary Number Theory". Thus I thought it would be nice to devote the last lecture before Christmas in each course to a talk on the numbers in music, together with practical demonstrations of these numbers on various flutes. Unfortunately, a proportion of the students in the first lecture were somewhat overly concerned about the problems of passing the exams at the end of the semester. I had the feeling that they were impatient about the fact that a lecture was being "lost" to mere music, rather than training them to succeed in the exam. The lecture wasn't a success. However it was well received in the second course where there were far fewer students, all of whom were well motivated to think about all aspects of elementary number theory. Thus I have decided to write this lecture up - in English - in a pdf file, which you can look at here.