In the song attached below the text is written in Middle English. I tried to guess the pronunciation but an advice from a native Engllish speaker would be appreciated. Thanks for your help
The honest answer is that British choirs and soloists use modern English pronunciation as far as possible. So yongë will probably be pronounced like modern English young /jʌŋ/ with an extra syllable. The choice of vowel for this extra final syllabic 'e' varies. At one time, there was a pronunciation guide for Britten's Ceremony of Carols which specified -y (as in happy, jolly, silly), and specifically transcribed yongë as young-y. I think that might be considered a bit dated now, so choirs would more likely use a schwa /ə/ or a very light /ɛ/ or /e/.
Thanks for your answer Of course I don't really care about the way people pronunced such text in the late middle age, it's just that HA sounds a sort of zzz for any syllable not registered as "modern English". I will follow your recommandation.