Make sure the lyrics in the notes match the format of the voicebank.
Here are some examples of how you would write the lyrics for various types of Japanese voicebanks.
CV romaji: [ka] [e] [ru] [no] [ u ] [ta] [ga]
CV hiragana: [か] [え] [る] [の] [う] [た] [が]
VCV: [- か] [a え] [e る] [u の] [o う] [u た] [a が]
CVVC: [- か] [a え] [e r] [る] [u n] [の] [o う] [u t] [た] [a g] [が]
If you'd rather not edit the lyrics one by one, there are a few ways you can automatically convert between formats.
iroiro: UTAU plugin with many useful functions, including hiragana/romaji conversion and CV to VCV conversion
僕の考えた最強のry Ver2
ux.getuploader.com
autoCVVC: UTAU plugin that can convert between CV, VCV, and CVVC
autoCVVC2.0配布所autoCVVCとは単独音・連続音・CVVC用のus
delta-kimigatame.hatenablog.jp
Presamp: UTAU processing engine that automatically converts notes without needing to run plugins. You can write the note lyrics as plain CV lyrics.
About Presamp This software allows you to use a CV UST with any Japanese voicebank, regardless of CV, VCV, or CVVC formatting.
tl.tubs.wtf
OpenUtau: Alternative to UTAU that includes many phonemizers for automatically converting lyrics to different voicebank formats, for many different languages
Open singing synthesis platform / Open source UTAU successor - stakira/OpenUtau
github.com