One writer has said: "Where there is simple and genuine thought, deep and sincere feeling, wherever the eye is single, the inflections of the voice are straight; a crook in the mind however is indicated by a crook in the voice."
Pitch is the key of the voice. A change of pitch is a leap from one key to another during silence. Inflection, as we have seen, is a gradual change in the key while the voice is speaking. The pitch or key depends upon the muscular tension of the vocal chords, which act like the strings of a musical instrument: the greater the tension, the higher the key. Muscular tension implies nervous tension and this is dependent upon the mental state. If the mind is calm, the nervous and muscular tension is normal, and the speaker uses the key habitual to him in his ordinary speech. If the mental state is one of excitement, the key is higher because of greater nervous and muscular tension. If, on the other hand, the mental state is one of depression, the key is lower because of relaxed muscular tension.
In The Defence of the Bridge (p. [206]) the Romans, seeing the danger of the heroes, are wrought up to a high state of nervous tension which finds its natural expression in the high-pitched voice:
"Come back, come back Horatius!" Loud cried the Fathers all. "Back, Lartius! back Herminius! Back, ere the ruin fall!"
Contrast with this the lower key of Horatius, who is calm and self-controlled:
"O Tiber! Father Tiber! To whom the Romans pray, A Roman's life, a Roman's arms, Take thou in charge this day!"
Observe the gradual rise in pitch with the increase of tension or excitement in the following:
And now he feels the bottom; Now on dry earth he stands; Now round him throng the Fathers To press his gory hands; And now, with shouts and clapping, And noise of weeping loud, He enters through the River-Gate, Borne by the joyous crowd.
In the following lines, where the Douglas holds communion with himself, the tension is low chiefly because of his great mental depression, and, consequently, he speaks in a low key: