Yes there is a way to combine the two! I did just that yesterday But you need to create suffixes for the extra vb if it doesnt already have them, the reason why its so easy to merge Teto's voicebanks is because her appends already come with them and all you gotta do just put them into one folder so.if your utau of choice's append has them then that's all you gotta do. Extras in voicebank throw setparam kinda off so I'd recommend going through their oto manually to get desired results! If not here's this effective way of adding suffixes to voicebank that saved me with yesterday >v> : download setparam -> go to tools -> change aliases -> renaming rule: %m(suffix you want) -> run for all wav files and you're done! You have updated oto and can now put the folder into the folder for their core vociebank or whatever! And if theyre multipitch don't forget to not remove the written pitch from the alias, it should be like: G3 ( yes if theyre multipitch you'll then have to write the suffix and pitch the sampel was recorded as in the ust so utau can recognize what exact sample you want ).

Teto english ust download