Guetta is himself evidently at a loss to grasp the significance of the empirical formula, "Listen and imitate." He seems however to be aware of an antagonism between imitation and mechanical vocal management. The reason of this antagonism has already been noticed, but it will bear repetition. For a teacher to tell a pupil to "hold your throat open and imitate my tone," is to demand the impossible. A conscious effort directly to hold the throat open only causes the throat to stiffen. In this condition the normal action of the voice is upset and the pupil cannot imitate the teacher's voice. This was the condition confronting the teacher of the second generation in the "maestral succession" just considered. He found his pupils unable to get with their voices the results which had come easily to him. Attributing his satisfactory progress as a student to the mastery of the supposed mechanical principles of tone-production, this teacher ascribed his pupil's difficulties to their failure to grasp the same mechanical ideas. As a natural consequence he labored even more energetically along mechanical lines. Curiously, no teacher seems to have questioned the soundness of the mechanical idea. Failure on the part of the pupil to obtain the correct use of the voice served only to make the master more insistent on mechanical exercises. In direct proportion to the prominence given to the idea of mechanical management of the voice, the difficulties of teachers and students became ever more pronounced. The trouble caused by throat stiffness led the teachers to seek new means for imparting the correct vocal action, always along mechanical lines. In this way the progress of the mechanical idea was accelerated, and the problem of tone-production received ever more attention. Faith in the imitative faculty was gradually undermined by the progress of the mechanical idea. With each succeeding generation of master and pupil, the mechanical idea became more firmly established. Something akin to a vicious circle was involved in this progress. As attention was paid in practical instruction to the mechanical operations of the voice, so the voice's instinctive power of imitation was curtailed by throat stiffness. This served to make more pressing the apparent need of means for the mechanical management of the voice. Thus the mechanical idea found ever new arguments in its favor, based always on the difficulties itself had caused.