For people who don't read music and don't know how to notate their vocal line, this might help.
SYNTHESIZER V uses a single-note MIDI melody to generate vocals. Anyone who has a recorded vocal (no backing) can use either BIAB or REALBAND to obtain a MIDI interpretation of that vocal. This could then be used in Synth V. I dare say that it won't be perfect but it will certainly give you a good head start that can be tweaked to get the vocal line that you want.
In BIAB it's called "Audio Transcribe" and it's found under "Audio" on the main men. It's also possible to use the "Transcribe" option found in Audio Edit in the "Edit" menu.
In REALBAND, it is done using "Generate | Generate Intelligent Audio Harmony" then selecting "Transcribe Audio to MIDI".
I have tried creating MIDI from a monophonic WAV in both Realband and BIAB and it worked fine.
I hope this helps,
--Noel
• my latest song: Every Single Day (a duet with Synth V vocaloids, Kevin & Natalie)