Most of the rank and file of the singing profession are fairly obsessed by the desire to cultivate a big voice. This obsession is a demon destroyer of voices; it makes so many singers force their voices and shout, and the result is that first the quality of the voice is spoiled, and then the voice is ruined entirely.

A powerful voice is a grand instrument and the possessor of one is most fortunate; but loudness alone will not make any one a success, so why should so much thought be given to power, and the possessor of a loud voice so much envied? As well might a violin envy the trombone!

The worst of the average striving after power is that, after a short period of loudness and shouting, the voice, if not ruined, loses what power it had, simply becoming dull and dead.

Power is a legitimate ambition; every one rightly wants to develop the voice to its maximum power of dramatic expression; but it is worse than useless to expect the voice to express more grandeur than the individual possessing it can feel.  True, we frequently hear loud, powerful voices, with no grandeur in them, but if the possessor of a voice of average size wishes to add to his power, he must accomplish this by the addition of grandeur.

Consequently, thought must be concentrated on what might be termed a legitimate obsession, and that is to develop a ‘big’ spirit.  Breathing and thought are the means, and as the spirit grows more expansive, the body responds and becomes stronger, and that means that the voice becomes more powerful. The voice must never be forced beyond its natural resonance, but the amplification of the various powers, bodily strength, and resonance, brings the voice to its maximum power.
Loudness of tone must never be the dominating thought, but greatness of spirit, and as stated before in this book, the voice will be found to be big enough to express any emotion felt by the singer, however great it is. His fame will then rest on being a ‘big’ artist, rather than on the possession of a ‘big’ voice.

Zay, William Henri. Practical Psychology of Voice and of Life. G. Schirmer, 1917.