But first, an aural example:

The “rumble” in the region immediately below the larynx detected in every voice by the investigators [the Old Masters], and of course in their own voices too, they promptly called voce di petto, chest voice. (This is readily noticed when holding a low note, produced naturally without overloading, and lightly tapping the bone structure just below the larynx with the tips of two or three fingers.) It is present on the low notes of all voices, male and female, and the series of notes concerned are the so-called chest tones because of their characteristic timbre. As the pitch rises so the laryngeal rumble gradually tends to fade away completely – because the mass of the cords gradually lessens. On the medium and high notes there is no rumble; tapping of the chest brings no response. Little or nothing escaped the ardent attention of our investigators. They concluded (rightly) from the above phenomenon that for the lowest notes, all voices, the whole of the vocal cords was engaged in length and depth, and the considerable fundamental vibrations communicated themselves to the bone structure near at hand with a resonance, or resounding, effect. N.B. It is incredible how the most unreasonable ideas about vocal technique and tonal colouring are spawned! For instance, certain teachers specialize in never allowing their female pupils  to produce the lowest notes – from E, first line, downwards, with the so-called “chest” quality, and instead get them to drag down the relatively poorer medium voice to overlap the “chest” (Puritanical modesty?). And to produce what? Just a miserable, weak, colourless hybrid sound. Thus ignorance abolishes one of the richest of natural tonal colours in the female voice. “It’s vulgar,” they say. Admittedly, but only if overdone. (So is lipstick and make-up, if slapped on.) Why not abolish the “chest” tones also of baritones and basses, and get rid of the lowest string of violins and ‘cellos. The whole idea is too stupid for words! For purposes of expression the greatest composers have always included certain low notes in songs and arias to be sung with this “chest” quality.

Who is right?

Herbert-Caesari, Edgar F. Tradition and Gigli: 1600-1955: a panegyric. R. Hale, 1963.