In Chapters II and III, I have already discussed historically the pronunciation of a in the United States—not, I fear, to much effect, but at all events as illuminatingly as the meagre materials so far amassed permit. The best study of the pronunciation of the letter today is to be found in George Philip Krapps excellent book, The Pronunciation of Standard English in America, from which I have, already quoted several times. This work is the first adequate treatise upon American phonology to be published, and shows very careful observation and much good sense. Unluckily, Krapp finds it extremely difficult, like all other phonologists, to represent the sounds that he deals with by symbols. He uses, for example, exactly the same symbol to indicate the a-sound in cab and the a-sound in bad, though the fact that they differ very greatly must be obvious to everyone. In the same way he grows a bit vague when he tries to represent the compromise a-sound which lies somewhere between the a of father and the a of bad. It is heard chiefly, he says, in somewhat conscious and academic speech, as a compromise between the former, which is rejected as being too broad, and the latter, which is rejected as being too narrow or flat. This compromise a, he says, is cultivated in words with a, sometimes au, before a voiceless continuant, or before a nasal followed by a voiceless stop or continuant, as in grass, half, laugh, path (also before a voiced continuant, as in paths, calves, halves, baths, when the voiced form is a variant, usually the plural, of a head form with a voiceless sound), aunt, branch, cant, dance, fancy, France, shant, etc. Later on he says that this compromise a-sound is the same that occurs in heart, star, large and Clarke, but this, it seems to me, is not quite accurate; there is a perceptible difference. The usual sound of a in heart is far nearer to that of a in father.
In any case, as Krapp says, this a-sound is commonly an affectation, save in New England, and, as we have seen, it originated as an affectation even there. The flat a, on the contrary, is widely distributed over the whole country, and may be regarded as the normal American a, as the a of father is the normal English a. No other difference separates the two dialects more sharply. Krapp notes the purist tendency to condemn [the flat a] and goes on:
The result has been to give to [the compromise a] extraordinary dictionary and academic prestige in the face of a strongly opposing popular usage. The reasons for this are several: first, that standard British speech and some forms of New England speech have [a broad a] in the words in question; second, that New England has exerted, and to some extent continues to exert, a strong influence upon formal instruction and upon notions of cultivation and refinement throughout the country; and third, that [the flat a] is often prolonged, or drawled, and nasalized in a way that makes it seem not merely American, but provincially American. To steer between the Scylla of provincialism and the Charybdis of affectation and snobbishness, many conscientious speakers in America cultivate [the compromise a]. The writer has tested this sound on many different groups of speakers from various sections of the country, and has never found one who used the sound who did not do so with a certain degree of self-consciousness. If the cult of this sound continues long enough, it may in time come to be a natural and established sound in the language. In the meantime, it seems a pity that so much effort and so much time in instruction should be given to changing a natural habit of speech which is inherently just as good as the one by which the purist would supplant it. Especially in public school instruction it would seem to be wiser to spend time on more important matters in speech than the difference between half and haalf.