I've been thinking about this a bit... I could create that Android app but it will be not very easy to make the site and the app interact seamless. What if the site took care of that. It would be nice if the site behaved like a decent audio player without downloading every vg(m/z) file every time. Obviously it would be hard to make it 100% perfect, it's still a site, I think the most annoying issue will be Android can decide to stop Chrome. Javascript takes a bit more performance but the past proved this will not be an issue. And it will be compatible for every device that can run Chrome or Firefox.
The storage API can be used to store the music on the host, the site could offer the option to add the whole game to the local storage and display if it's in already. The site itself can work offline as well using
https://developers.google.com/web/progressive-web-apps/