HVPT is of course only part of the solution; I hope I didn't make it sound like a cure-all. Being able to distinguish the phonemes that you hear is just the fir

HVPT is of course only part of the solution; I hope I didn't make it sound like a cure-all. Being able to distinguish the phonemes that you hear is just the first step, and it should logically be followed by learning to produce the sound distinctions in question yourself. And it is definitely a two-way feedback loop in that the better you hear the differences, the better you produce them, and vice versa, just as it is for infants learning their native language. So a more complete training method would combine HVPT with ways to have your own pronunciations scored to see how well you are producing the sounds of the target language. This is I feel a relatively neglected part of non-native language education, and it is very common for people to have spoken a non-native language for years without learning to distinguish native sound pairs. So good luck with your efforts to help people learn better, and I hope you share the results with us.