Utter the standard English sound of a in hat, for which the sign is [æ]. Say several times [ɑ æ] and watch the tongue as you do so; you will see that it moves forward and is a little higher in front and lower at back for [æ]. The opening of the mouth is often quite as large for [æ] as for [ɑ].
Now try to produce the sound which lies between the two, with the tongue occupying an intermediate position; you will obtain the sound [a], which is the northern English vowel in hat, and the vowel in the French word chat; in standard English it occurs only as the first part of the diphthongs in bite [bait] and bout [baut].[43] This [a] is sometimes called the "clear" a sound. See the diagram on p. [123].
Next, draw the tongue a little back, and you will obtain a variety of [ɑ] which is "dark" and has a suggestion of the vowel in all [ɔːl]. This sound is commonly substituted for the "pure" or "neutral" [ɑ] in cockney speech, so that fast is made to sound like [fɔːst], park like [pɔːk].
This "darkening" of the a sound should not be permitted; in order to counteract it, it may be advisable to make the class utter [ɑ] singly and in chorus, until they are quite clear as to the nature of the required sound.
It is sometimes found that precise speakers, through an excessive desire to avoid any suspicion of cockney leanings in their speech, substitute [a] for [ɑ], saying, for instance, [faːðə] in place of [fɑːðə]; it is particularly ladies of real or would-be refinement who commit this mistake. A mistake it is, like every other deviation from what is generally recognised by the educated.
In other cases the "clear" pronunciation of a is often heard, e.g., in glass, bath, past, answer, demand, grant, everlasting. Both [a] and [æ] occur, particularly in the speech of ladies. What is the American pronunciation of half?
In standard English there is practically no short [ɑ],[44] but only the long [ɑː], which should be neither "dark" nor "clear." If we analyse it carefully, we often find[45] that it is not a single vowel of uniform value, only the first part being "pure" [ɑ], the rest being a faint variant; but for practical purposes we may regard it as uniform in quality, as in good speech it is a pure long vowel.
38. There is a short sound closely akin to it (in position, but not in sound), which we have in but, much, etc., and for which the sign is [ʌ]. The back of the tongue is raised a little in the production of this sound, and sometimes the front also; and in consequence there are several varieties of it. It occurs only in syllables having some stress; we have [ʌ] in teacup, unfit, until; but not in welcome, which is not felt to be a compound. When it is unstressed, it becomes the dull vowel [ə]; unstressed but is [bət]. Observe the vulgar pronunciation of just as [dʒest].
The dull vowel [ə] occurs very commonly in ordinary speech; most unstressed syllables contain this vowel or the variety of mentioned below. It is found, for instance, in the italicised syllables of vowel, variety, carpenter, ordinary. The long [əː] is variously written; we have it in fern, fir,[46] fur, word. (In northern English there is some variety in the [ə], according to the written vowel which it represents.) Notice the precise and the ordinary pronunciation of such words as paternal, polite, potato. The uneducated often insert [ə] in such words as Henry [henəri], umbrella [ʌmbərelə]; and sometimes they substitute for [ə], as in miracle, wrongly pronounced [mirikl̩], philosopher, wrongly pronounced [fi´lɔsifə], and in oracle, pigeon.