Board Thread:Questions and Answers/@comment-27885184-20151217203229/@comment-26968107-20151217204736

Do you mean "interface" of the software? VOCALOID1 is English only, VOCALOID2's interface language depends on what Vocaloid you buy (for example, if you buy Miku the interface will be Japanese, but if you buy SONiKA it will be in English), VOCALOID3 and VOCALOID4 has both English and Japanese interfaces, I guess.