Creating a Virtual Singer VSTi

You can use Birchlabs JuicySFPlugin to manually assign the voices, but it's a pain in the neck to use. That is the way it is now with Musescore 4 unfortunately. But your app sounds amazing.

I'm kind of looking something similar, so far as I can tell there seem to be a few approaches:

1. Create a custom instruments.xml with a custom Staff Text + CC mapping to change phonemes and a MuseScore plugin that automatically generates the phoneme Staff Text based on the lyrics (https://musescore.org/en/handbook/developers-handbook/references/instru…). But, I'm not quite clear how well MS4 supports it. https://musescore.org/en/node/334701#MIDI_mapping_and_MIDI_CC

2. MIDI 2.0 also has Flex Data Messages which can be used to send lyrics. However, phonemization probably needs more than a single syllable to work nicely -- the plugin based approach would be able to look at the full text. Similarly, I'm not quite clear how well VST3 supports it -- VST3.7.9 does seem to have a kTextTypeID and kPhonemeTypeID, but the latter also has a TODO attached to it.

3. There seems to be something called MusePlaybackEvents in MS4, but there doesn't seem to be much documentation on it. https://musescore.org/en/node/325860, https://github.com/musescore/MuseScore/pull/9610, https://github.com/musescore/MuseScore/projects/40, https://github.com/musescore/MuseScore/tree/master/src/framework/mpe

From these, approach 2. seems the least amount of friction involved. i.e. MS4 sends lyrics data using text events to VST and then VST processes them as necessary.

That's an amazing idea!
Do you have some news about it? Is the integration proceeding?

That would really be a breakthrough!

I will say this since this an old post from Jun 2023, now its March 2024. VST's are not the way how Musescore Studio is developing things. If you want to get dedicated sound synthesis to be able to be in Musescore Studio then you should do a collab with developers of Muse Sounds by Muse Group. So you'll need to contact them. From what I heard on your Cantamus website, this synthesis technology really competes with Synthesizer V (what was used to create Hatsune Miku music recordings). If anything you have to email the Muse Group. Someone from Musescore studio devs said this on Discord on March 2024 and I quote:

"
If they want to integrate this with MuseScore, they have two options:

Option 1.
Step 1. Release it as a VST. Users would need to enter the lyrics into the VST manually.
Step 2. Optionally, contribute code to MuseScore so that MuseScore can automatically transfer the lyrics to the VST.

Option 2. Contact the Muse Sounds team and see what they are willing to do.

To my knowledge they haven't done any of these things yet, but I don't know everything that happens in the Muse Sounds team, so maybe they did reach out. But I don't know and probably nobody will know because the Muse Sounds team is not known for being very generous with development updates.

Building this technology into MuseScore is not an option (unless they make all of it open-source), since it's not possible to package non-GPL3(-compatible) stuff with MuseScore. (That's also why Muse Sounds need to be installed separately using Muse Hub.)", Casper Jeukendrup, Musescore Studio developer.

It's only to your team to do what you can. Honestly I'd prefer if you worked in collaboration with Muse Sounds team from Muse Group as it will give a much better result, but its entirely up to you.

Kind regards.