What was the magic formula used by the masters of the seventeenth and eighteenth centuries in producing those marvelous singers about whom historians so delight to rhapsodize? That they produced great singers is beyond question, but as to possessing a secret which has been lost nothing is further from the truth. The so-called secret may be discovered by any one who will study the works of such Italian masters as Tosi, whose book was published in 1725, and Mancini, whose book appeared in 1775. Their secret may be briefly told. First, these men were musicians. They knew music. They were men of fine musical taste, and particularly sensitive to tone quality. Their ideals of tone quality and artistic singing were very high, consequently they set a high standard for their pupils. What was their method of realizing their ideals in their pupils? In other words, how did they teach? They knew nothing of vocal physiology and make no reference to mechanism further than that of dividing the voice into two registers, chest and falsetto, making the latter synonymous with head voice. They developed the upper voice out of the light register. Their sensitive ears would stand for no forcing and most important of all their pupils has daily lessons of an hour each for five, six, or eight years. The great secret of the Italian method then was that pupils were under the guidance of a sensitive musical ear every day in the year.
Clippinger, D. A.. “The Old Italian Method”, Etude Magazine, March 1913 : 209.