This doesn't sound like a Vocal synth at all. I'm a little sus. I've never worked with Ruby but I've worked with Gumi and their other song sounds like the vocals are being changed in some way, heavily auto tuned or just mixed with an other voice. All of her vowels are way too smooth especially when she goes go go go. The only phoneme that does that exact sound naturally has a slight choppiness right in the middle of its recording. If this is real its impressive but I would need to se a UST VSQ or VSQX to really be convinced otherwise. The description makes me think this was made with a new AI since it says "trained with real vocal stems". @parallax_fifths what do you think?