i finished the oto on this bank but how do i know it's good
Play a UST using the voicebank and listen for whether any notes are off-time. Make sure to clear the preutterance/offset/STP from the note properties first.
i thought about making a multipipitch voicebank but i don't know at what note i should record it? ( default pitch is c#3)
First, decide what range you want the voicebank to have. If you want it to cover your full vocal range, you need to check the highest and lowest notes that you can comfortably sing. One way to do this is by putting notes in UTAU, playing them, and trying to sing the same pitch.
Then, decide how many pitches you want to record. If you have more pitches, it'll match the tone of your voice more accurately. If you have less pitches, you will have to do less work recording and OTOing the voicebank.
You can use UTAU as a visual tool to determine which pitches to record, Put in notes for the high and low limits of the range you want, and as many notes in between as pitches you want to record. Assuming you want to keep the C#3 pitch, change the pitch of one of the middle notes to that. Then you can space out the other notes to evenly cover the area between the high/low limits.
For example, let's say the range you want is G2 to A4, and you want 3 pitches total. So there's three notes in the middle, and they're evenly spaced out like this.
Evenly spaced out notes assumes that your voice smoothly changes tone from low to high. However, there are some special circumstances you may want to account for, such as the difference between chest voice and head voice, or falsetto. It's okay to have pitches that are closer together if those are necessary to capture the changes in your voice at those points.