At least until recent times, doubleTwist worked incorrectly with non-ASII characters. Android itself works perfectly with Unicode, including Unicode in ID3 TAGs. I have a lot of Russian songs and naturally use Cyrillic in song names, albums, artist and other tags, as well as in folder/file names. It works fine on Windows and works fine on any Android phone, if you synchronize media manually. But doubleTwist produced garbage. When I asked about it on doubleTwist forum no one even bothered to answer.