Careful study of the clarinet demands a rudimentary knowledge of the physical principles involved in producing its sound. We tend to satisfy ourselves with the knowledge gained from private study or the instinctive, trial by error process that has taken us a long way in our journey to become excellent clarinetists. But if we pause for a moment to ask why the solutions we have discovered over the years work, we take some of the mystery away and can perhaps solve future problems in getting ourselves further along in both the technical and musical study of the clarinet. This study of the physical principles is a responsibility we have to ourselves and to our students.