The liner notes of this 1967 album explain it pretty comprehensively, so I’ll just paste them here:
Americans Speaking is a recording prepared by the National Council of Teachers of English to provide teachers and students with large-scale samples of some of the major varieties of American English, as naturally used by educated speakers. It is the first record to provide samplings of this scale since the inauguration of the Linguistic Atlas project in 1930; thanks to the evidence of the various regional atlases, it has been possible to select speakers whose pronunciation is characteristic of wide and identifiable dialect areas. All speakers recorded represent the cultivated speech of their areas: each had had some college education at the time the recordings were made, and some were postgraduates; no speaker exhibited pronunciation features widely regarded as substandard in his own area.
To permit larger samples than most records of this type provide, only six specimens are given, three from the North, two from the Midland, one from the South, following the regional designations first used by Hans Kurath in his Word Geography of the Eastern United States (Ann Arbor, 1949).
- Eastern New England (Topsfield, Massachusetts)
- Brooklyn, New York
- Inland Northern (Madison, Wisconsin)
- The Delaware Valley (Philadelphia, Pennsylvania)
- South Midland (London, Kentucky)
- Prattville, Alabama
It is noted that three of the speakers are from the area of the original settlement where local divisions are discussed in the Word Geography. The other three—Inland Northern, South Midland, Southern—come from areas of secondary settlement for which there is as yet no detailed analysis like that in the World Geography or in Kurath and McDavid’s Pronunciation of English in the Atlantic States (Ann Arbor, 1961); nevertheless, the evidence suggests that the three principal dialect regions extend west of the Alleghenies and even beyond the Mississippi, with clearly marked subareas.
The fact that these six specimens appear on this record must not suggest any judgment that these are the only models for good American pronunciation. Many others exist-from the older areas, for example, Pittsburgh, Richmond, Charleston; from newer ones, Chicago, Cincinnati, St. Louis, New Orleans, San Antonio, San Francisco, Portland, Salt Lake City, and Denver. It is to be hoped that this record will be but the first of a series which will provide teachers and students with an understanding of the many varieties of cultivated American English.
The selection for each speaker is in two parts: (1) a set text read aloud and (2) a sample of free discourse.
The set text, composed by Mrs. Celia M. Millward of Boston University, was designed to give examples of three types of pronunciation features:
- Differences in the pronunciation system. Does fought have the same vowel as lot, or a different one? Does morning have the same vowel as car or as ford, or are they different? Does Tuesday have a (y) glide following the (t)? Does whetstone have an (h) at the beginning?
- Differences in the phonetic quality of the vowels and consonants. Do you notice differences from your own speech in the pronunciation of (ai) in five, (au) in out, and the stressed vowels of rode, paper, week, murder?
- Differences in the occurrence of particular vowels and consonants. Does greasy have an (s) or a (z) sound? Does creek have the vowel of seek or that of sick? Does sister have the vowel of sick or something else? Does laugh have the vowel of grand or that of father?
In addition to the set passage, each speaker talked informally about some topics of interest to him, and from each of these unrehearsed recordings a selection was made. The topics are diverse: small town life in Kentucky and New England, childhood on an Alabama plantation, a philosophy of teaching, developing the craftsmanship of the professional writer, the duties of a specialized National Guard unit. What all the passages have in common is the fact that the subjects were of such interest that the speakers were unconcerned about how they were talking. From these passages one can observe several aspects of oral communication: (1) possible differences from the pronunciation of words as read; (2) the reduced contextual pronunciations of auxiliary verbs (have, will, are), prepositions (to, of), conjunctions (and, or); (3) the conversational patterns of intonations, stress, and word transitions—and the ways these may differ from the patterns found in reading aloud; (4) some evidence on the complex orchestration of speech that scholars now call paralanguage…
- Inland Northern: “My Eccentric Grandfather”
- Inland Northern: conversation
- South Midland: “My Eccentric Grandfather”
- South Midland: conversation
- Eastern New England: “My Eccentric Grandfather”
- Eastern New England: conversation
- Alabama: “My Eccentric Grandfather”
- Alabama: conversation
- Brooklyn: “My Eccentric Grandfather”
- Brooklyn: conversation
- Delaware Valley: “My Eccentric Grandfather”
- Delaware Valley: conversation
Linguistics fans out there should also check out the International Dialects of English Archive.