Well, enough of all this theorising. I just put on a very excellent record of the Boat Band performing "Bayou Teche Waltz", the vocal sung by JC Gallow, the black creole musician from Mamou,Louisiana. His pronunciation is approximately ba-you, with the "ba" intermediate between the "ba" of standard English back, and the longer a of a sheep going "bah". However, this "a" sound is only the start of a diphthong which changes to the short "i" of "in" before the "y" of "you". Broadly speaking, if you said ba-i.you very fast you'd have it. Mind you, that's black Mamou pronunciation. Who knows what a white cajun would say in Church Point?
   
The record is "Back Deck Blues" by the Boat Band, a double CD, extremely good value, and available from Harbourtown Records or any good shop.HARCD 036.