I love reading about the history of the English language. If I have 20 minutes to fill in my rhetoric class, I can give an impromptu lecture on that history, which I title (to myself) as “Why the English Language Is Like a Club Sandwich.” But never having formally worked with the International Phonetic Alphabet in a linguistics class, I never felt that I truly comprehended the “Great Vowel Shift” that marks part of the transition from Middle to Early Modern English.
Thanks to the Web, this site, by Melinda Mezner of Furman University in Greenville, South Carolina, makes it all comprehensible. Read the IPA text, listen to the sounds. After that, the diagrams might make more sense. Warning: lots of small sound files to download.