The only uvn to tvn conversion or export we know about, is potential export of different audio samples from Yamaha Tyros music workstations, often for the purpose to edit these in some kind of editors or audio tools.
We have not found anything in particular about this conversion, except that sample converters, such as the Translator Professional, list it as supported. If you need further assistance with this type of export, perhaps Yamaha support or some kind of online community can help.
Updated: October 6, 2023