Sentence:  It is no very difficult matter to be loud in a high tone of voice; but to be loud and forcible in a low tone, requires great practice and management; this, however, may be facilitated by pronouncing forcibly at firſt in a low <WSD>monotone</WSD>; a <WSD>monotone</WSD>, though in a low key, and without force, is much more ſonorous and audible than when the voice ſlides up and down at almoſt every word, as it muſt do to be various. 
Meaning of the word marked with <WSD> tags:  A single unvaried tone of speech or a sound.