Merely to assume that a method of treating the registers which has given, apparently, good practical results in the hands of one teacher is sound, and rests on a scientific basis, is unwarranted. It may be simply a little better or a little worse than some other. How is the student to distinguish, in his choice, between Mr. A and Mr. B, in the case of two successful teachers, both of whom recognize registers? A physiologist may be sound as far as he goes, yet lack that practical knowledge of the voice which the vocal teacher properly considers requisite in determining how a pupil shall use the registers. Among those who are most dogmatic on this and other questions there is often a plentiful lack of knowledge of the vocal organs; and some clever laryngologists must have learned, when they were carried into the discussion of this subject, that some knowledge of music and singing is absolutely indispensable, and that enough cannot be picked up, even by an able man, in a few minutes devoted to interrogating singers, especially when these vocalists have been trained by widely different methods, and have, as is too often the case, given but little real _thought_ to the scientific, or, indeed, any other side of their art. We find "break" confounded with "register," and the meaning attached to the latter, at best, one-sided or inadequate in some respects. The truth is, such a subject cannot be settled by the physiologist, even when a laryngologist, as such; nor can the solution to a scientific question of this kind be given by a singer, as a singer. Such a problem can only be settled, as we have throughout insisted, by those possessing many qualifications, and even when the investigator unites in himself every intellectual qualification, something will depend on his temperament and spirit. An atmosphere of controversy is not favorable to scientific investigation, and among the dangers that ever lie in the path of the teacher are pride and prejudice. The assumption that one is prepared to teach is too often associated with views and feelings that prevent the guide from remaining himself a student and being ready to learn even from the very beginner, as he must if he have the true spirit. Unfortunately, several of the most highly qualified writers on this subject have formulated their views under conditions unfavorable to the attainment of the whole truth. It is to be borne in mind always that a register implies (1) a series of tones of a characteristic clang, _timbre_, color, or quality; (2) that this is due to the employment of a special mechanism of the larynx in a particular manner. It follows that in thinking of registers scientifically, one must take into account both the tones and the mechanisms by which they are produced.