I received some useful feedback on my vowel pronunciation on the first half of Farmer Duck. Essentially in English our vowels are not pure, our mouth moves as we utter them, gliding effortlessly from one vowel to another. However, in Bengali, although there are diphthongs, most vowels sounds are pure. The key to getting this right is not to move your lips as you make the sound (kind of like whistling). I tried this and found it a monumental effort. Not primarily because the sounds are unfamiliar (I hear and replicate these in French) but because the muscles you seem to need to use are in me very weak. I would go so far to say it hurts my mouth. It must be lack of practice. It’s just that feeling of pushing forward your lips and then holding them still. But there again I tried making some similar sounds in French just now and my mouth felt very relaxed even though my lips were pushed forward. This is bizarre!
I think that some other good advice is taping pieces having listened to a native speaker’s rendering of them (though as I explained I did have this but have lost the electronic file!) So the pieces in the third section of Teach Yourself Bengali may be good or any poetry recordings on line.
Must get taping and I will post you on it when I have!