Some time ago I posted “A Guide to the Pronunciation of General American English“. Recently, I came across a useful adjunct: “North American English Dialects, Based on Pronunciation Patterns“.
If you scroll down the page, you’ll find a list of links to samples of the speech patterns of various regions. I was amused to hear Larry Page, a co-founder of Google, in this YouTube video clip. It’s almost like hearing myself — another native of the central and southeastern parts of Michigan’s lower peninsula.
What that clip and others illustrate is that a broad pattern of pronunciation (e.g., General American English) is overlaid with many sub-regional variations in the form of accents and emphases.
Larry Page’s accent, for example, has a nasal and breathy (or reedy) quality. He might say TOE-MAY-TOE instead of TOE-MAH-TOE, but the way in which he says it will be different than the way it sounds coming from the mouth of an Iowan.
Further, in many parts of the Upper Midwest (certainly including parts of Minnesota, Wisconsin, and Michigan) there is a tendency to end a sentence on an ascending tone, as if a question were being asked even though the sentence is declarative. Again, the sentence may end with TOE-MAY-TOE instead of TOE-MAH-TOE, but it will have a distinctly different sound than TOE-MAY-TOE placed elsewhere in a sentence and TOE-MAY-TOE pronounced at the end of a sentence by an Iowan.