Clara Kathleen Rogers

Born with dual American and British citizenship and raised in Germany, Clara Kathleen Rogers (1844-1931) essayed the operatic stage under the name of Clara Doria in Italy for several years after studying with the highly respected voice teacher Antonio Sangiovanni in Milan for two years. 

A five year sojourn in England as a concert artist was followed by her return to America and subsequent tenure as a professor of singing at The New England Conservatory.  Rogers wrote quite a few books which had a wide influence, among them Your Voice and You: What the Singer Should Do (1925). The following passage from Your Voice and You is relevant to other posts I've made on singing and the ear. 

Chapter III

How to Train the Ear to Perceive Different Qualities of Tone

You say you are not sure that you know the difference between a tone that is properly produced and one that is not; that you are uncertain, when practicing, what sort of sound you should expect to hear; that you are therefore working in the dark. That is somewhat discouraging as coming from a singer who aspires to be an artist. But do not despair, because it does not follow, necessarily that you are lacking altogether in that indispensable endowment musical sense. It shows, however, that you have never accustomed yourself to analyse sounds, and your lack of auditory discrimination may be due simply to that.

You ask what you can do about it? If your ear fails to acquaint you with those subtle difficulties in tone-quality on which the development and the perfecting of your voice depends, must you give up all hope that you can succeed as a singer? No, certainly not yet; not till you have striven to overcome your dullness of perception- and failed!

You can train your ear to perceive the different qualities of tone by listening with conscious intent to detect those differences. Acquire the habit of listening intelligently to both musical and unmusical voices instead of simply hearing them. If you follow up this habit persistently, with undivided attention, your ear will gradually become analytical enough to stand you in good stead for modifying the sounds of your own voice.

The ear is to the singer what the eye is to the painter of draftsman. If you would succeed in any branch of Art you must develop your powers of observation till they become keen and true. It is wonderful, for instance, what the trained eye can see that the untrained eye is blind to. The painter sees a variety of colors in a rock which to you or me may appear only gray. The mariner, when at sea, can tell whether that dark gray streak you note horizon is a shore-line a cloud, or a fog-bank. The habit of observing intelligently has made it easy for him to distinguish at sight between three things which to you and me all look alike. Yet at the start that sailor had probably no better natural eyesight than either of us.

With the ear it is the same; you can acquire auditory faculties which you had no idea of ever possessing if you will set about forming the habit of listening with concentrated purpose to note the peculiar differences between one kind of sound and another; to analyze in what the pleasing or unpleasing quality consists in the different voices you hear. You will then soon become aware of the pleasing or displeasing elements in your own voice, and as soon as you reach that point you will instinctively modify your tones to your own satisfaction. Not only will you succeed in perfecting your voice but you will also immeasurably enrich your enjoyment of music in all its form by the increase of sound perception thus acquired.

You should understand, when we speak of the ear as the controlling medium of voice, that it is not the ear itself that determines the kind of sound we produce; the ear simply informs the mind and it is the mind which dictates the tone stimulated through the auditory nerve.

But let me warn you against one thing. There are those who will tell you that no one can hear how his own voice sounds. Do not heed them, for there never was a great fallacy proclaimed! On the contrary we have, or should have, a twofold sensitiveness to our own tones, for we hear them both subjectively and objectively. If you have no consciousness of the way your voice sounds you may be sure that there is something wrong with you.

When I read the passage above, I am reminded of Dr. Alred Tomatis who maintained that there was a great difference between hearing and listening, the former being a passive process while the latter an active one.  Like Rogers, Tomatis also asserted that the ear can be trained, and in going further, even rehabilitated. 

Rogers touches on a matter which Tomatis devoted a great deal of attention, and that is the two modes in which vocal tone is perceived.  Rogers uses the terms subjective and objective, while Tomatis uses the scientific processes of bone conduction and air conduction.  As such, bone conduction is felt (stand in the shower, close your ears, and you will 'feel' the sound of the water on your skull), which is a subjective phenomena, while air conduction is - in contrast - objective insofar as being heard outside the body.  Both avenues become refined in the active listener, engendering greater quality of tone.  

Unfortunately, Your Voice and You isn't available on the web yet, but you can find Roger's other books here.