Early Middle English was standardised around 1425 by clerks to the chancel courts. The dialect they used came from the East Midlands and was essentially that of Chaucer. Here is the text for the picture on the home page.
A SHIPMAN was ther, woning fer by weste: For aught I woot, he was of Dertemouthe. He rood up-on a rouncy, as he couthe, In a gowne of falding to the knee. A daggere hanging on a laas hadde he Aboute his nekke under his arm adoun. The hote somer had maad his hewe al broun; And, certeinly, he was a good felawe. Ful many a draughte of wyn had he y-drawe From Burdeux-ward, whyl that the chapman sleep Of nyce conscience took he no keep. If that he faught, and hadde the hyer hond, By water he sente hem hoom to every lond.
Sound changes that became thus fixed in the spelling included the novel phonemes [z,v] and the stops [k,g]. The stops (or plosives) in MnE are in three pairs: POP, BOB; TAT, DAD, KICK, GIG. The third pair are made against the velum, and this seems to be problematic for speakers of Germanic languages, perhaps when they have colds. Here is a video of what the vocal tract does to produce the [k] sound: http://www.youtube.com/watch?v=hSqjNOaQyDE. Closing the airflow at the velum seems to be difficult. The [g] sound is the same, except that it starts with voicing. These images compare the vocal tract for the two sounds:
SLTs distinguish harsh, breathy, normal and falsetto voicing. The following video illustrates the fourth mode.
Old English had phonetic spelling and Alfred imposed a West Saxon pronunciation standard, but [k] and [g] were already changing! The following passage shows how WS scribes used the annotations ċ and ġ to show current pronunciation.
Can you pronounce these words as the locals do? Göteborg (Swedish); saga (Swedish); Belgie (Dutch); Scheveningen (Dutch); guide morgen (Dutch); chäs-chüechli (Schwyzerdeutsch); chunt (Schwyzerdeutsch).
By the 12th century ME was borrowing loanwords from its Danish speakers. Many of these were conservative from the shared Proto Germanic ancestor. For example, an OE scip was now captained by an OD skipper.