Odd pronunciation of adjectives ending in -ed

I am currently listening to an audiobook reading of Keats poetry by Sir Ralph Richardson, and I have noticed a peculiar pronunciation of adjectives ending in -ed. While I have heard in the past certain words like winged being pronounced as wingid rather than wingd, I thought it an archaic peculiarity of a small subset of words. Yet today I have heard Sir Richardson pronounce stained in the same odd fashion, as steinid rather than the overwhelmingly more common steind. It has made me think and wonder whether this oddity is some sort of literary remnant from the past, or perhaps just a mistake from his part.

For copyright purposes I cannot link to the recording, but if I haven't made myself clear, you can hear what I'm talking about in this publicly available reading of Annabel Lee by Poe.

"Annabel Lee" - Edgar Allan Poe (Poem Version) on Youtube (0:54)

Solution 1:

In Shakespeare's time, many words ending -ed were pronounced the modern way, with just /t/ or /d/, but many words we pronounce today with /t/ and /d/ were pronounced with /-ɪd/, and for many words, both pronunciations were acceptable.

Shakespeare took advantage of this to make his poetry scan, and often indicated the pronunciation (for those which could be pronounced either way) by spelling them either mask'd or masked.

By Keats' time, the pronunciation was much closer to the modern version (I don't know whether it was exactly the same), but poets still took advantage of the archaic pronunciations to make their poetry scan, indicating the pronunciation in the same way that Shakespeare did. Keats did this extensively, while Wordsworth seems to have used this quite rarely, if at all.