I watched a YouTube clip of Elina Garanca, a mezzo gaining in popularity, that was shared with me by a colleague. My feeling is she makes an accepted sound, which is to say a modern approach to imitating the sound of the great singers rather than a true vocal tone. To my ear it sounds artificially dark and lacking in an equal amount of brilliance. A true tone is balanced in both dark richness and vibrant brilliance. Chiaroscuro. Resonance and squillo. If you observe her mouth and tongue position and imagine the position of the tone, they are all too dark in an attempt to artificially recreate the natural depth and back position of a well functioning voice. When there is no unvocalized breath escaping through the glottis it makes the vowel feel like it has moved right to the back of the throat and even down to the larynx. Modern singers have too much air through the glottis to have that placement naturally so they “open” the throat(actually constrict) by yawning to compensate for the forward placement their function would normally result in. That is how the majority of singers, even at the highest international level, sing now because it is how they have been taught and is even what is expected.