Regional dialects in English are largely informed by the particular way people in different geographic areas make their vowel sounds. Consonants can inform the sounds of vowels, but are largely static; going from an “F” sound to a “T” sound is a huge leap, whereas vowels are a little bit fluid, bleeding into each other. The entire game is to make sure you have enough difference between vowel sounds so that words can be distinguished from one another. But the specific sounds you make? Not so important, as long as they get the idea across of what word you’re trying to say.
A key change in the California Shift is what’s called the cot/caught merger. Northeasterners and Midwesterners pronounce those words differently, giving the former an “ah” sound and the latter an “aw” sound. “Californians do not,” says Eckert, who is originally from New York. “They have no idea. That vowel is almost completely merged. Think ‘mawwm’ instead of ‘mom.’”
Vowel sounds work like those sliding puzzle games where you have to unscramble a picture by sliding one piece of it at a time. As soon as you move one piece, you’re left with an empty space behind you, which has to be filled by something else. Californians dropped the “cot” vowel sound, pronouncing it like “caught” instead. So something had to fill that space. “The California Shift is this kind of combined change in the pronunciation of short vowels,” says Kennedy. The easiest way to think about it? Look at the words kit, dress, and trap. In the California Shift, “kit” becomes “ket”, “dress” becomes “drass”, and “trap” becomes “trop”.
—Dan Nosowitz writing for Atlas Obscura about the linguistics behind the “pop punk voice” employed by bands like Blink-182.