An Introduction to Diastole
Diastole (etymologically from Greek, also known as “ectasis”), is a rhetorical device which consists in lengthening out a vowel soundOpens in new window or syllableOpens in new window that is naturally short.
In other words, a syllable naturally short, is made long; for example: “Oooooh yeah!”. Diastole is the opposite of systoleOpens in new window.
Diastole is sometimes employed for the sake of meterOpens in new window, and may result (in English) in the shifting of accent from one syllable to another. — (Silva Rhetocae)