In training the voice, the teacher should commence with the chest register: and this from the fact, that where the chest and medium registers play into each other (in the manner shown) the voice is weak and uncertain, and it is an extremely difficult matter to strengthen and equalize it. But this equalization is just the important task to be accomplished. The method to be pursued is this: – the tones which are common to both the chest and the medium registers, must be practised alternately with each. For, just as the skilful workman, who would join two pieces of wood and make the strength at the point of adjustment equal to the rest, will dove-tail the two, by extending the end of one sufficiently far in upon the end of the other to prevent any weakness at the extremities; so the skilful teacher will extend the limit of one register into the middle of the next, until the weak tones of both are blended and become equally sound and strong – the point of contact being smoothed and obliterated altogether.

Bassini, Carlo, and Stephen F. Austin. Bassini’s Art of singing: an analytical, physiological and practical system for the cultivation of the voice. Plural Pub Inc, 2007.