MUTA is a relatively new Synthesizer developed in China. Currently, it is in 0.2 Alpha, with the only voice being Yan Xi (嫣汐). You can download it in the description of the demo song above!
Here's a tutorial by Giraffey:
Personally, I've found MUTA a little frustrating to use, but it produces great results and I fully recommend people try it! Also Yan Xi is perfect in every way//// *shot*